A cell is placed into a 1 millimolar solution of substance X. Over time you witness the concentration of X inside the cell increase to 5 millimolar. Describes the movement of substance X?

X is moving into the cell by active transport

Explanation:

According to Oxford dictionary;active transport refers to ''the movement of ions or molecules across a cell membrane into a region of higher concentration, assisted by enzymes and requiring energy''.

Since the concentration of X is higher inside the cell than it is outside the cell, energy must be required in order to move substance X across the cell membrane against existing concentration gradient. This process is called active transport.