请问:下面句子中的红色部分做什么成分？

1. But writing is not his only hobby.

2.He likes playing volleyball , too.

3.For many of us,gardening is a good way to relax.

4.I brought the parents for you.

5.She felt very sorry for what she did.

6.There were so many activities for every age.

请问：下面的句子中的that是否可以省略？划线部分是不是表语从句？

My favourite part of the hotel was that there was a swimming area with dolphis.

谢谢！！