在比較兩種遊戲對孩童影響時
原句老師加進了that of的用法
我上網查了一下
還是不太清楚這邊是否一定要加進that of或that in文法才正確
想請教版內高手，謝謝!
1.
我:
Childern's emotion after playing LEGO is better than playing online games.
師改:
Children's emotion after playing LEGO is better than that of playing
online games.
2.
我:
The sense of satisfaction in those who played LEGO is lower than those
who played online games.
師改:
The sense of satisfaction in those who played LEGO is lower than that in
those who played online games.

that of = children’s emotions of playing online gamesthan前後比較的東西必須要一致children’s emotion （前句）沒辦法跟playing onlinegames做比較（後句）

感謝樓上~~~原來如此阿另外想請教that後面的介詞，第一句的that of 可以改成that after嗎?第2句的that in可以變成that of嗎?再次感謝~