题目

Once, on a cold day in September, when I was very little, my big sister _________ me to a beach not far from our house.Near the beach there was a tidal(受潮汐影响)island, which _________ that when the tide goes out, you can walk to it, _________ when the tide comes in again, you can't get to it. Mum and Dad _________ let us go there.When we _________ the beach, the tide was out. My sister _________ going to the island.But Mum and Dad said we couldn't. It's _________! I said.Don't worry, said my sister. I'll _________ you. Trust me.I was a bit _________, but the island looked very nice in 化学与人体健康密切相关。市场上有“高钙牛奶”、“加氟牙膏”、“葡萄糖酸锌”等商品，这里的“钙、氟、锌”应理解为 A．原子          B．单质          C．分子          D．元素