Opposing pairs of muscles involved in movement are called a. tendons and ligaments. b. flexors and extensors. c. smooth and striated muscles. d. skeletal and cardiac muscles.

b. flexors and extensors

Explanation:

The flexor and extensor muscles are skeletal type muscles. They have the function of joint movement for which they work together, they bend and straighten the joints of the body.

Flexors work to bend a joint and extenders extend and straighten joints

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.