They reduce pregnancy because the delay the uterus releasing the egg, and delay ovulation. Less than 1% of women who use IUDs pregnant, although pregnancies after the emergency contraceptive pill are not as rare.
The answer is c i believe
This is referred to as DOMS, Delayed Onset Muscle Sorenes. The exact mechanism is not understood, but DOMS appears to occur due to connective tissue microtrauma.
