Question

choose the best idea to add to a summary of \a village on the move.\ the people of newtok were forced to leave their town. erosion caused by the rising river has made newtok unsafe. there used to be a lot of permafrost in alaska. frozen soil under the ground, called permafrost, is melting.

Explanation:

A summary should focus on the main idea of the text. The first two options are about Newtok, which is likely the main subject of "A Village on the Move." The third option is about Alaska in general, not specifically related to the village. The fourth option is a detail about permafrost but doesn't directly relate to the village's situation as much as the first two. Between the first two, the second one explains the reason (erosion from the rising river) why the village is on the move (unsafe), which is more comprehensive for a summary.

Answer:

Erosion caused by the rising river has made Newtok unsafe.