b
(b) Density of cork $= d$, Density of water $= \rho$
Resultant upward force on cork $ = V(\rho - d)\,g$
This causes elongation in the spring. When the lift moves down with acceleration a, the resultant upward force on cork $ = V(\rho - d)(g - a)$ which is less than the previous value. So the elongation decreases.
