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Run-ons and comma splices — ACT practice questions

Run-ons and comma splices on the ACT English test cover two independent clauses joined with no punctuation or with only a comma. A student has to spot those fused sentences and pick a revision that uses a period, a semicolon, or a comma plus a coordinating conjunction without creating a fragment. Questions usually underline a stretch of a passage and ask which option makes the sentence most grammatically acceptable. Answer choices shuffle punctuation and joining words, and common traps include keeping the comma splice, pairing a semicolon with and, or adding a period that leaves a dependent clause stranded.

  • Section: English 50 questions on the paper
  • 60 practice questions in the app

Sample questions

Listening to Walls

When caretakers of old masonry halls need to learn what lies behind a wall, drilling exploratory holes can damage the very surfaces they hope to preserve. Echo tracing offers a gentler approach. In a brick lecture hall scheduled for restoration, the crew works room by room, listening along each plastered wall before any opening is cut. A light wooden striker sends vibrations through plaster and stone. Because solid masonry returns a sharp sound while a hollow chamber produces a softer one, technicians can make an identification of the location of1 sealed doorways without opening the wall. The survey begins with a chalk grid drawn across the wall.2 One technician moves the striker methodical3 from square to square while a second records each change in pitch. A reliable survey requires workers marking the grid, to compare nearby sounds, and estimating each hollow area's size4. When a doubtful patch needs review, site supervisor Lena Ortiz joins mason Carlos Ruiz, and Carlos and she5 repeat the sequence.

Consistency matters more than force. Every striker is returned to their6 labeled slot, since differences in weight can alter the sound. Technicians also reject any striker who's handle7 is loose. Each echo appears as a shaded cell on the map, the team8 adds notes about nearby windows and beams. These notes help distinguish an actual chamber from ordinary variations in the wall's construction. A dark band beside a window may look like a sealed doorway until the notes show that the shading simply follows a timber that has always belonged to the frame.

An isolated dark cell does not prove a cavity several neighboring cells must9 form a coherent outline before the team recommends closer inspection. Even then, the map is a guide rather than a verdict. Behind similar dull responses, there is often several explanations10: an empty flue, a timber brace, or a deliberately filled doorway. Only careful comparison with the visible structure allows the crew to interpret what the wall seems to say.

Question 1

Which choice makes the sentence most grammatically acceptable?

  1. ANo Change
  2. Bmap the team
  3. Cmap; and the team
  4. Dmap; the team
Show answer

Answer: D — map; the team

The clauses on both sides of the marked portion can stand alone as sentences, so a semicolon can join them. A comma alone creates a comma splice.

Question 2

Which choice makes the sentence most grammatically acceptable?

  1. ANo Change
  2. Bcavity. Several neighboring cells must
  3. Ccavity, several neighboring cells, must
  4. Dcavity; but several neighboring cells must
Show answer

Answer: B — cavity. Several neighboring cells must

The original joins two independent clauses without punctuation, creating a fused sentence. A period after “cavity” correctly separates the clauses into complete sentences. The comma choice incorrectly sets off the subject, and the semicolon with “but” adds an illogical contrast.

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