Triggering of the muscle action potential occurs after:. i. acetylcholine binds to chemically-gated channels in the motor end plate.
ii. calcium ion binds to channels on the motor end plate.
iii. acetylcholinesterase is released from synaptic vesicles into the synaptic cleft.
iv. the action potential jumps across the neuromuscular junction.
v. Any of these can produce an action potential in the muscle cell.

corona the outer atmosphere of the sun, temp. may reach 2,000,000 c

chromosphere middle layer of the sun's atmosphere

photosphere visible surface of the sun

convection zone layer of the sun which energy travels by convection from the radiative zone to the photosphere

radiative zone layer of the sun which energy is transferred away from the core by radiation

core very dense center of the sun

nuclear fusion process by which tow or more low-mass atomic nuclei fuse to form another, heavier nucleus.

radiation when energy is transferred as electromagnetic waves

convection the process in which heat is transferred by the circulation or movement of matter

differential rotation the way the sun rotates, rotating faster at its equator than at higher latitudes

sunspots dark areas that form on the surface of the sun

solar flare an explosive release of energy that can extend outward

prominences huge loops of cool gas that extend outward from the photosphere

not too sure but maybe in the hot springs.

b is the correct answer