1. which sentence contains an error in subject-verb agreement? elke or carina is going to be the new dance squad captain. july and august are the warmest months of the year. each volunteer and staff member need to arrive at the scheduled time. some of her friends and family members are coming over for dinner. which sentence contains an error in subject-verb agreement?

Each volunteer and staff member need to arrive at the scheduled time.

Explanation:

The adjective each is used before a singular countable noun, and, therefore, the verb should be singular, too.  

So the sentence should be written as "Each volunteer and staff member needs to arrive at the scheduled time."

All the other sentences contain no errors in subject-verb agreement.

- "a nonrestrictive clause functions as a modifier to a noun (that is an object, person or concept). these clauses can be described by the following three options: it is set off by comas, it contains a subject and a verbs and it adds nonessential information to the sentence.

for example, in "here is bill gates, who confounded microsoft software company" we can identify "who confounded microsoft software company" as a nonrestrictive clause modifying the noun bill gates. this clause can be describes as a nonrestrictive clause because it is separated by a comma, it adds nonessential information to identify who bill gates is and it must contain both a subject (who) and a verb (confounded)."