The number of software engineers ________ increasing every year.

A. is

B. are

C. has been

D. have been

Detail: 

A collective noun refers to a group of people or things that is treated as a single entity in speech. Committee is a collective noun. A committee is made up of multiple people, but the word itself is singular in form. In American English, collective nouns take is. In British English, collective nouns can take is or are.