The number of software engineers ______ increasing every year.

1. are
2. have been
3. has been
4. is

Explanation: The number of + Plural noun +—+ Singular Verb + ext. অর্থাৎ The number এর পরে Plural noun হবে কিন্তু singular verb বসে। যেমন- The number of boys present in the function was satisfactory.
আবার, A number of এর পরে Plural noun এবং verb টিও Plural হয়। যেমন- A number of students have joined together to form a club for hockey fans.