Regarding this question
Which of the following are correct regarding active transport?
ATP is necessary and sufficient for active transport.
ATP is not necessary but sufficient for active transport.
The relative concentrations of the material being transported have little impact on the rate of active transport.
Transport proteins are necessary and sufficient for active transport.
Active transport relies on transport proteins that are powered by an electrochemical gradient.
A. The answer is option 3 , but why it can’t be option 2 as we know active transport usually uses ATP(not always so there is no necessity) ?
B. And also what is the meaning of sufficient in this question?(does it mean it is not necessary but it provides enough energy or it means active transport only needs ATP and no need for transport proteins )