题目

The little boy entered the house, unhappy. His mother was_______cakes in the kitchen. She smiled as she turned round but_______when she saw his face. Tyler, _______happened? Is everything okay?Nothing is okay, Mom, said the boy, Today, in our science lesson, Mrs. Green was_______ the environment.She said that the whole world is getting dirtier and that many animals and plants are dying. She wants us to think of something we can do to help. I thought all the way home, but there is_______ I can do to make a difference.Let me tell you_______, the mother said after thinking for a while. One mornin下列叙述中，错误的是A．原子半径：Na＞Mg＞O 　B．13C和14C属于同位素C．0族元素是同周期中非金属性最强的元素D．N和P属于第ⅤA族元素，HNO3酸性比H3PO4的强