Which statement about earthquakes is accurate? select the two correct answers.
about 100 earthquakes per year are strong enough to cause damage.
a few hundred earthquakes per year are strong enough to be detected by instruments.
more than 1 billion earthquakes happen per year.
most earthquakes are not strong enough to be felt by humans.
fewer than 100,000 earthquakes happen per year.

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).