A cell has a membrane potential of -100 mV (more negative inside than outside) and has 1,000 times more calcium ions outside the cell than inside. Which best describes a mechanism by which Ca2+ enters this cell?a. facilitated diffusion of Ca2+ into the cell down its electrochemical gradientb. movement of Ca2+ into the cell through an ion channel down its concentration gradientc. passive diffusion of Ca2+ into the cell down its electrochemical gradientd. cotransport of Ca2+ into the cell with Cl-e. movement of Ca2+ into the cell through a carrier protein down its electrical gradient

When two ions are transported simultaneously across the plasma membrane through a channel protein, then this of membrane transport is called co transport.

According to the given question the concentration of Ca2+ is 1000 times more in outside the cell than inside.

As a result the Ca2+ ions will be transported from its high concentration region that is outside the membrane to its low concentration region that is inside the membrane.

But the important thing to note that in every circumstances the negative resting potential should be maintained.So to maintain the normal negative resting membrane potential same number of Cl- ion will be be transported inside the cell by co transport mechanism.