There_______ a limit on the number of times an aircraft tire can be retreaded.

• A. Is
• B. Are
• C. Has
• D. Is not

Answer: (D)

In sentences that start with there to express existence, the verb to be must agree with the noun that follows. Here the noun after there is a singular noun, limit, so the verb should be singular. When you want to say that no such thing exists, you attach not to that verb. So the correct filling is is not, giving: There is not a limit on the number of times an aircraft tire can be retreaded. This uses the proper singular form and the negation.

The other forms don’t fit because they would either mismatch number (are with a plural noun) or use an incorrect auxiliary for this existential construction (has isn’t appropriate here), or express a positive existence rather than negate it. In everyday speech you might hear There isn’t a limit, but There is not a limit is the fully correct, non-contracted version.