Q.9-

A student says: "I've been knowing him for 7 years?" How do you respond?

Topic Area
Stative verbs

How to respond...
Most English verbs can be categorized as Stative (those which convey a 'state' or an 'emotion') and Non-Stative (those which convey a dynamic, non-stative action)

Stative verbs (like, hate, believe, know, understand, etc) are not normally used with a continuous/progressive tense. In the example above, the student does not appear to know this - hence the mistake.