Question

语法: 复合句什么时候加连词？

this sport looks like two people are fighting。
it starded as a fun activity for young people who wanted to try something different from skiing.
为什么上一句不带WHO，下一句又带呢？

Answer 1

1）及物动词后可以加宾语从句，整个宾语从句相当于一个宾语
2）主句与从句之间应该是接关系代词或关系副词，不是连词，连词是连接句与句，短语与短语，词与词的，如果用了连词那就不是复合句而是并列句了
3）that用在名词性从句里，名词性从句包括主语从句、宾语从句、表语从句和同位语从句四种，这四种后就要用that，在宾语从句中that可省