what is the LCM of 4a and 10a(squared)?

A. 2a

B. 4a

C. 20a(squared)

D. 30a(squared)

And also we need to choose one of the wrong answers and tell why someone might make a mistake and choose it.

i also need the right answer!

so:

1: i need the right answer

2:i need a wrong answer and describe how someone could accidentaly choose it!

thanks

and BTW this isnt for school my family wants to know it! =)

thanks again