All living things contain carbon. Which of the following statements are true about carbon atoms? 1. Each carbon atom can form single bonds with up to four other carbon atoms
II. Each carbon atom can form double bonds with up to two other carbon atoms
III. Carob atoms can join together to form chains or rings
IV. A single molecule of some compounds can contain thousands of carbon atoms

Choose the incorrect statement (a) the motor end plate membrane is only capable of generating graded potentials, but it is contiguous with the skeletal muscle sarcolemma, which can generate action potentials. (b) propagation of an action potential through the t-tubules into the sarcoplasmic reticulum triggers the release of ca++ into the cytoplasm of a skeletal muscle fiber. (c) the generation of suprathreshold endplate potentials in multiple muscle fibers could be due to the increased frequency of action potential generation at the axon hillock of a single motor neuron. (d) a greater amount of ach would be found in the presynaptic vesicles of a motor unit that fired several action potentials after exposure to botulinum toxin, than in a motor unit that fired several action potentials after exposure to the venom of the krait snake (which contains α-bungarotoxin).