Which choice completes the text so that it conforms to the conventions of Standard English?
A
allows
B
are allowing
C
have allowed
D
allow
Explanation
Correct answer: A.
Choice A is the best answer. The convention being tested is subject–verb agreement. The singular verb “allows” agrees in number with the singular subject “landing.”
Why the other choices are wrong
Choice B
Choice B is incorrect because the plural verb “are allowing” doesn’t agree in number with the singular subject “landing.”
Choice C
Choice C is incorrect because the plural verb “have allowed” doesn’t agree in number with the singular subject “landing.”
Choice D
Choice D is incorrect because the plural verb “allow” doesn’t agree in number with the singular subject “landing.”