Stress is the momentary stress that occurs in response to life experiences

The momentary stress which occurs because of the experiences of one's life is the 'acute stress'.

Acute stress is the psychological condition which is the most common form of stress. The pressure and demands of the life induces acute stress in people, which is beneficial in small doses. When the person is too much stresses it may take tool on his health and affect his abilities.

Hence, the blank can be filled with 'acute'.

a. to encourage apoptosis

that would be called plucking : )

explanation:

''plucking, also referred to as quarrying, is a glacial phenomenon that is responsible for the erosion and transportation of individual pieces of bedrock, especially large "joint blocks". as a glacier moves down a valley, friction causes the basal ice of the glacier to melt and infiltrate joints (cracks) in the bedrock."