Question

subject - verb agreement
subject - verb agreement means the subject and predicate in a sentence must agree in number.

• subject: who or what the sentence is about
• predicate: what the subject is doing (action)

singular
subject - does not end in \-s\
verb - ends in \-s\
plural
subject - ends in \-s\
verb - does not end in \-s\
multiple singular subjects
\and\ - plural verb form
\or\ - verb should agree with the nearest subject
exceptions:

• collective nouns: words that act as a singular noun while representing a group
• indefinite pronouns: pronouns that do not explicitly denote a number of subjects
• some singular subjects end in the word s but are not plural. (e.g. \politics\)

which sentence has correct subject - verb agreement?
rain were coming down in droves.
snow are falling from the sky.
leaves are falling from the trees.

Explanation:

• For "Rain were coming down in droves", "rain" is a singular subject (exception: some singular subjects end in "s" but are not plural). The correct verb should be "was" (singular verb form) instead of "were" (plural verb form).
• For "Snow are falling from the sky", "snow" is a singular subject. The correct verb should be "is" (singular verb form) instead of "are" (plural verb form).
• For "Leaves are falling from the trees", "leaves" is a plural subject (ends in "s"). The verb "are" is a plural verb form, which follows the subject - verb agreement rule (plural subject + plural verb).

Answer:

Leaves are falling from the trees.