A spring tide can occur O A in any month after March.
0
B. in March, April, or May.
O
C. in late February to early June.
D. in any month of the year
D. in any month of the year.

many other transport proteins, often called pumps, move materials against a concentration gradient. active transport drives molecules across a membrane from a region of lower concentration to a region of higher concentration. this process, shown in figure 5.1, uses transport proteins powered by chemi- cal energy.