An experimenter measures the length of a rod. Initially the experimenter and the rod are at rest with respect to the lab. Consider the following statements.
(A) If the rod starts moving parallel to its length but the observer stays at rest, the measured length will be reduced.
(B) If the rod stays at rest but the observer starts moving parallel to the measured length of the rod, the length will be reduced.
The new length is given by,
Where, l0 = Length of rod at rest
` c = Speed of light >> v
As v << C
⸫ 
<1
Thus, l<l0
Consider the rod at rest and observer moves with the speed of v then the new length is given by,
Where, l0 = Length of rod at rest
` c = Speed of light >> v
As v << C
⸫ 
<1
Thus, l<l0
Thus, the length will be reduced in both the cases.
So, correct option is C.