题目

·Put sunscreen (防晒油) on before going out in the sun. ·Take it with you. ·Use it — after a swim. — every hour or so while playing outdoors. — if you get sweaty. ·Cover up when the sun is overhead — 10 a.m.—2 p.m.. — especially at lunch time. ·Get your suntan (晒黑) gradually and not too much. ·Controlled exposure (暴露) to sunshine helps avoid skin cancer. Ask your chemist to recommend a suitable sunscreen. Queensland Cancer Fund P. O. Box Spring Hill, QLD.4000 Phone (07) 8397077 Provided for community awareness by the Queensland Cancer 54. This passage is mo13、下列计算正确的是（　　）A、3+x=3xB、x+x=x2C、3a2b-a2b=2D、a2+a2=2a2