Elinvar, an alloy used in precision instruments, hair springs for watches, etc. contains the following element as principal alloying element

Answer: Option D

Elinvar is a nickel-iron alloy notable for having a modulus of elasticity which does not change much with temperature changes.
Elinvar originally consisted of 52% iron, 36% nickel, and 12% chromium.
It is almost non-magnetic, and corrosion resistant.