要不要by 都行,句子意思一样.不加by ,themselves作同位语,加by ,by themselves在句子里作状语
by oneself 独自地,单独地
还可以说成
They were proud that they themselves had built the house
要不要by 都行,句子意思一样.不加by ,themselves作同位语,加by ,by themselves在句子里作状语
by oneself 独自地,单独地
还可以说成
They were proud that they themselves had built the house