Answer:
Na+ only
Explanation:
Depolarisation of membrane refers to the change in the resting membrane potential of the membrane of a cell which is usually -70mv to a more positive value.
This value changes when the positive ions move inside the cell which increases the positive charge inside the cell.
In the myocardial cell, the sodium ions move inside the cell which changes the potential towards the more positive side as a result of which the signals for contraction arises.
Thus, Na+ only is correct.
The answer is excretory system
The mix of salt and fresh water forms a brackish water environment.
