Which is a complex sentence?

AThe technician installed my hard drive and turned on my computer.
BAfter you install the security software, your computer will run smoothly.
CMy computer is lightweight, powerful, and portable.
DBoth computers are powerful, but this one is less expensive.

Verified Answer :

A complex sentence is a sentence which has one independent clause  and with at least one dependent clause. From the choices given, the best answer is B. The independent clause would be "your computer will run smoothly" and the dependent clause would be "you install the security software".

Answer:

The answer to your question would be that "after you install the security software, your computer will run smoothly" is a complex sentence.

Explanation:

A complex sentence has at least one dependent clause (a) and one independent clause (b). The difference between a dependent and independent clause is that the latter can stand alone as a sentence as it represents a complete thought.

a) *After you install the security software,

b) your computer will run smoothly.