It is Saturday morning. The sky is blue. My father and I are going to the park. There are a lot of people in the park. Some children are running on the grass. A dog is running after them. Some men are sitting on the grass. They are talking. Two girls are flying a nice kite. Three women are standing under a tree, and they are watching the children playing. There is a boat in the lake and two women are boating. Everyone in the park is very happy.

当a比15多b时，用等式表示是a=15＋b．

设阿伏加德罗常数为N_A，则下列说法正确的是（   ）

对人说话有____、正确使用____用语会给生活带来的和谐和快乐。