When they go back to America,they show the photos to their friends.

问题描述:

When they go back to America,they show the photos to their friends.

如果?是打错了话,这个句子能通。
一回到美国,他们就把照片拿给朋友们看。

当他们返回到美国,他们把照片展示给他们的朋友看!

应该填will,表将来。由句意可知:当他们回到美国,他们将会把照片给他们的朋友们看。用将来时

填will
他们回到美国后,会把照片给朋友们看。

When they go back to America,they will show the photos to their friends.