4. Where does a magnetic field occur in relation to an electrified wire. a At either end. but no in the middle
b. Only on the side closest to the source
of electricity
c. Around the entire length of the wire
d. Only on the side furthest frou the source of electricity

maybe A or b

Explanation:

the abdomen (less formally called the belly, stomach, tummy or midriff) constitutes the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. the region occupied by the abdomen is termed the abdominal cavity. the stomach secretes acid and enzymes that digest food. ridges of muscle tissue called rugae line the stomach. the stomach muscles contract periodically, churning food to enhance digestion. the pyloric sphincter is a muscular valve that opens to allow food to pass from the stomach to the small intestine.

answer: substrate concentration. enzymes work best when there is a high enough substrate concentration for the reaction they catalyse.