How have cactuses adapted to the fact that it almost never rains in the desert?
A
They're covered in spikes.

B
They have thick, pleated stems.

C
They have big, waxy leaves.

D
They're camouflaged.

option a is correct i.e.

explanation:

in context to the membrane of nerve impulse, the outer membrane of neuron is semi permeable that is only sodium ions can pass through the membrane i.e. smaller ions can pass through the membrane while larger ions cannot pass through it.

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which

what is a measurement of the earth’s history divided into time periods?

> fossil record <

sedimentary rock

> geologic time scale <

radioactive elements

i believe your answer would be c.. : )