根据句意和空缺处所给首字母写单词。答案书写于规定的位置。

1. I have m________hobbies, such as swimming, rowing and hiking.

2. He said he would never f_________ the trip to Mount Fanjin.

3. We should do more exercise to keep h ________.

4. Tongren have developed r           into a modern city in the recent years.

5. My little sister is so young that she can't look after h________.

某核素^A_ZX的氯化物XCl₂ 1．11g配成溶液后，需用1mol/L的硝酸银溶液20mL才能把氯离子完全沉淀下来，则

（1）X的质量数为__________

（2）若X的核内中子数为20，55．5g XCl₂中所含质子的物质的量为__________mol。