Final answer:
The release of Ca++ from the SR during muscle contraction takes milliseconds.
Step-by-step explanation:
According to the information provided, the release of Ca++ from the sarcoplasmic reticulum (SR) occurs during the latent period of a twitch, which is the first phase of muscle contraction. During this phase, the action potential is being propagated along the sarcolemma and Ca++ ions are released from the SR. The duration of the latent period can vary depending on the muscle type, but it generally lasts for a few milliseconds to 100 milliseconds. Therefore, the correct answer is b. Milliseconds.