Which element provides strength to the exoskeletons of clams and oysters?
a) sulfur
b) oxygen
c) hydrogen
d) phosphorus

phosphorus

Explanation:

provides strength

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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.

straight or amphibians are homeothermic to thermal