Select the correct sequence of the following events during muscle relaxation.
(a) Pumping Ca²⁺ into sarcoplasmic cisternae
(b) Thin filaments move away from M line
(c) Restoration of the length of sarcomere
(d) Masking of myosin-binding sites on actin

During muscle relaxation, Ca²⁺ is pumped into sarcoplasmic cisternae and results in the masking of active sites on actin filaments. This causes the return of ‘Z’ lines along with attached thin filaments back to their original position. The thin filaments slide from the M line. This restores the length of the sarcomere.