A cotransporter is something that moves two substances across a membrane, one passively and the other actively. The Na+/ K+ ATPase transports sodium and potassium ions across the plasma membrane against their concentration gradients. This pump is not considered a cotransporter because

both ions are transported actively

Explanation:

If both ions are being transported against their concentration gradients, then they are both being transported by active transport, as it requires energy.

A co-transporter moves two substances across the membrane, one passively and one actively. But in this case neither ion is moved passively, so it cannot be considered a cotransporter

when atoms of different types of elements join together, they make molecules called compounds. water consists of compound molecules made up of 2 hydrogen atoms and 1 oxygen atom. this is why it's called h2o. water will always have 2 times the number of hydrogen atoms as oxygen atoms.