Activity 1 Before you read,complete the sentences with the words at the top.rn1.A () is a thin beam[光线] of light that can do very small,careful work.rn2.A () is extremely small and found inside atoms.rn3.A way used to help sick people is called ().rn4.Something with many parts that is difficult to understand is ().rn5.The smallest part of a plant or animal is called a ().rn6.When doctors () someone,they help them to get better from injury or sickness.