An appropriate exercise to develop muscle endurance for the ________ is ________ .

Knee flexions (leg curls) train the knee flexors, primarily the hamstrings, not the quadriceps, which are knee extensors - the exercise and muscle group are mismatched.

Arm curls (bicep curls) train the elbow flexors (biceps brachii and brachialis), not the triceps, which are elbow extensors - the exercise and muscle group are mismatched.

Wrist curls performed with the forearm pronated and flexing the wrist against low resistance directly and isolatedly target the wrist flexor muscles (flexor carpi radialis and flexor carpi ulnaris). Using low resistance for 15 repetitions aligns with the endurance training prescription of higher reps and lower load, making this the only option where both the exercise and the named muscle group are correctly matched.

Half-squats primarily recruit the quadriceps and gluteus maximus through hip and knee extension, not the hip abductors (gluteus medius/minimus), which require lateral movement such as side-lying hip abduction or lateral band walks.