Sodium and potassium ions are essential for muscle contractions of the heart. the ions are transported using a pump, which obtains energy by the breaking of . this action requires the expense of energy. so, sodium and potassium ions are transported .

1:  The ions are transported using a pump, which obtains energy by the breaking of ATP.

2:This action requires the expense of energy. So, sodium and potassium ions are transported using Active transport.

The mechanism described in the question, in which muscles of the body are contracted through the process of active transport.

The process needs input of energy because it involved movement of potassium and sodium ions against the concentration gradient. The energy is obtained  by the breakage of ATP bonds to make the process possible.

Active transport can occur through two ways:

1: Pirmary:

In this way, ATP molecule is directly used for the transportation of molecules across a membrane.

2:Secondary:

In which ATP is not directly involved in pumping or ions across the membrane.

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the element that provides strength to the exoskeletons of clams and oysters is phosphorus.

this is so because calcium carbonate is the main component in the shells. calcium carbonate is strengthened by phosphorus.

explanation:

correct answer is a. and d.