Which form of the verb is correct?

the news occasionally reports about people who have seen the core, or center, of a tornado
a. contains
b. contain

#1  sara was always tasked with selecting birthday presents for her friends and family because everyone admired her  impeccable taste. 

impeccable (adj): perfect, flawless

#2  they moved to the united states many years ago, but their  insular  attitudes made it difficult for them to socialize. 

insular (adj): isolated; separate

#3  the professor explained the  semantic  relationship between the two nouns used in the sentence. 

semantic (adj): related to words or the meanings of words 

happy to : )

the positive connotations of the words "pretty," "quiet," and "silence" give the excerpt a tone of nervousness. i think its this