Your answers aren't complete. A microscope should be carried by the arm with the other hand under the base.
http://www.google.com/search?q=microscope+carry&tbm=isch&tbo=u&source=univ&sa=X&ei=-wM2UpGTNI61qAHBs4H4DA&ved=0CEAQsAQ&biw=711&bih=453&dpr=1
Which part of the microscope should you use to carry it?
a. the stage
b. the eyepiece
c. the focus knobs
d. the arm
Is it the arm?
5 answers
So, what is the best answer in the given options?
Your answer -- the arm -- is the only choice that's even partly right.
yes the arm is the correct answer
A and B