Read the sentence. one of the assistants on vacation. which verb form correctly completes the sentence?

The answer is: is.   There are many assistents, but only one is on vacation. The correct form of verb that completes this sentence is the simple present of the verb to be, used in the third person of singular: he or she.

Simple Present of Verb to be

Infinitive: be

I am; she/he/it is; you/we/they are.

One assistent is on vacation.

The assistents are on vacation.

- "about the claims : -

making a claim is just a fancy way of saying that you're stating your main point.' claims are not just opinions. a claim tells what you think is true about a topic based on your knowledge .

about the country claims : -

a counterclaim is just the opposite of a claim. counterclaims are also provable and supportable by reasons and evidence. not just, 'because i said so.' when you're planning an argument, you need to know what the counterclaim might be so that you can make sure that you disprove it with your reasons and evidence your research." - (catherineroberts)