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Semicolons and colons — ACT practice questions

On the ACT English test, Semicolons and colons asks a student to choose the punctuation that joins complete clauses or introduces a list or explanation. The student must tell independent clauses from fragments, place a semicolon between complete thoughts or among complex list items, and use a colon only after a complete clause. Questions typically underline a mark and ask which option fits the grammar of the sentence or which option most clearly sets up what follows. Traps include a semicolon before a coordinating conjunction, a colon after an incomplete opener, and treating a comma or period as interchangeable with either mark. Answer choices usually cycle through those punctuation options.

  • Section: English 50 questions on the paper
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Sample questions

A Dock That Rises with the Tide

At Marlow Inlet, low tide often left the fixed ferry landing more than a meter above the water. Port engineer Inez Park designed a floating dock that could slide vertically along four guide pilings. Before construction, her crew logged a complete tide cycle and marked the highest drift line on the seawall. The crew measuring1 the channel depth at six points and compared the findings with the design drawing. They prepared three temporary guides. survey stakes, alignment cables, and painted level marks.2 Together, the measurements showed where the dock could move without touching the muddy bottom.

At dawn the following week, a pile driver arrived on a work barge. By sunrise, workers had drove3 four steel pilings through the silt and into firmer material below. Each piling passed through a padded collar on the dock frame, allowing vertical motion while limiting sideways drift. During a rising-tide trial, the crew left the deck unloaded. The tide continued to rise; the platform followed without binding against the posts.4 A carpenter then installed the hinged gangway connecting the shore to the deck.

Park expected that the flexible gangway will remain5 within its safe slope as the tide changed. One concern remained, the shore-side hinge could twist if two corners rose at different rates.6 Workers tested that risk by shifting forty-kilogram sandbags across the deck. Load sensors recorded the weight at each corner. Because aluminum expands7 slightly in direct sunlight, Park repeated the measurements after the deck cooled in late afternoon. The second readings differed by less than two millimeters.

Although the first alignment looked level; a laser reading showed one corner was six millimeters high.8 Technicians inserted a thin spacer beneath that collar and repeated the tide trial. By the time the safety inspector arrived, all eight flotation chambers had seal9 by the technicians. The inspector distributed twenty-four water-filled barrels across the platform. The dock settled seven centimeters but remained above its required freeboard mark. The dock passed the load test, therefore, the crew removed the temporary braces.10 During the next ferry arrival, the platform rose with the wake and returned smoothly to level. Passengers could step aboard without the old landing's steep low-tide drop.

Question 1

Which choice makes the sentence most grammatically acceptable?

  1. ANo Change
  2. B: survey stakes, alignment cables, and painted level marks.
  3. C; survey stakes, alignment cables, and painted level marks.
  4. D survey stakes, alignment cables, and painted level marks.
Show answer

Answer: B — : survey stakes, alignment cables, and painted level marks.

The complete clause “They prepared three temporary guides” announces the three guides that follow. A colon properly introduces that list. A period leaves the list as a sentence fragment. A semicolon cannot join a clause to a fragment. Omitting punctuation fails to mark the explanatory noun-phrase list that follows.

Question 2

Which choice makes the sentence most grammatically acceptable?

  1. ANo Change
  2. B, the platform followed without binding against the posts.
  3. C: because the platform followed without binding against the posts.
  4. D the platform followed without binding against the posts.
Show answer

Answer: A — No Change

The rising tide and the platform's response are expressed as two closely related independent clauses. The semicolon correctly joins them without a coordinating conjunction.

Question 3

Which choice most clearly introduces the remaining concern?

  1. ANo Change
  2. B: the shore-side hinge could twist if two corners rose at different rates.
  3. C; because the shore-side hinge could twist if two corners rose at different rates.
  4. D the shore-side hinge could twist if two corners rose at different rates.
Show answer

Answer: B — : the shore-side hinge could twist if two corners rose at different rates.

The complete clause “One concern remained” prepares readers for a specification of that concern. A colon correctly introduces the possible twisting of the hinge.

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