A tetanic contraction produces more force than a single twitch because:
a. The levels of calcium in the sarcoplasm of the skeletal muscle stay higher for longer during a tetanic contraction.
b. A maximum number of myosin cross bridges are interacting with the thin filaments during a tetanic contraction.
c. The sarcoplasmic reticulum does not release calcium during a single twitch.
d. The binding sites on the thin filaments that the myosin heads attach to stay exposed for longer during a tetanic contraction.