Which of the following is critical to the function of most exoskeletons, endoskeletons, and hydrostatic skeletons? a. Muscles interact with the skeleton in antagonistic groups. b. Muscles attach to each of these types of skeleton via tendons. c. Muscles extend joints by pushing skeletal elements. d. Segments of the body or limbs are extended when paired muscles relax in unison.

Verified step by step guidance

1. Identify the common feature among exoskeletons, endoskeletons, and hydrostatic skeletons: All these skeletons provide structure and support to the organism, and they work in conjunction with muscles to facilitate movement.
2. Analyze the options: Consider how muscles interact with different types of skeletons to produce movement. Muscles typically work in pairs where one muscle contracts while the other relaxes, creating movement at a joint.
3. Evaluate option a: Muscles interact with the skeleton in antagonistic groups. This means one muscle of the pair contracts to move the skeleton in one direction, and the opposing muscle contracts to move it back, which is a fundamental mechanism in all types of skeletons.
4. Compare with other options: Option b is incorrect as not all muscles attach via tendons in all types of skeletons (e.g., hydrostatic skeletons do not have tendons). Option c is incorrect as muscles generally pull, not push, skeletal elements. Option d is incorrect as it is not typically the relaxation of paired muscles that extends body segments, but rather the contraction of one muscle in the pair.
5. Conclude that the correct answer is a: Muscles interact with the skeleton in antagonistic groups, which is critical for the function of exoskeletons, endoskeletons, and hydrostatic skeletons.