Why is a microscope used to observe bacteria? ?

A phase contrast microscope uses an optical technique that works by the use of a device to read the difference in thickness of the subject affecting the phasing of light resulting in a high contrast image. Staining bacteria also help microscope users to see bacterial structures that would have otherwise been invisible to the naked eye.

u=13

v=30

s/t=u+1\2at

=13+431/2

=13+265.5

=278.5

i believe the answer would be:

d. violin, clarinet, french horn, and tuba