[单选题]
A compound microscope is designed to resolve objects which qsp3y+(ksqy )are 0.010 mm apart ,o0er0d+79jt wnaik g. If the focal length of the objective is 4.0 cm and the wavelength of light used is 550 nm, who0 0jeg,r 7 tidak+9nwat is the diameter of the objective?
A. $0.27 \; mm$
B. $0.54 \; mm$
C. $2.7 \; mm$
D. $5.4 \; mm$