[填空题] It’’s never too early to (36) ________ your skin—or your children’’s—from the sun. The sun produces (37) ________ rays—(38) ________ A (UVA) and ultraviolet B (UVB) —that can cause short - and long—term skin damage. The immediate effects of harmful (39) ________—(40) ________, photosensitive (41) ________, and cell and (42) ________ damage—are bad enough. But (43) ________ experts believe that (44)________________. Health experts also believe that UVA may weaken the immune system. (45)________________. Using sunscreens regularly on children, for example, can reduce their risk of skin damage later in life. Sunscreens provide some protection by blocking the sun’’s rays on the skin. They are labeled with a sun protection factor (SPF): (46)________________. But no sunscreen totally blocks the sun’’s rays.