Solution:The above statement is true.
It is good to sleep under a tree during the daytime because during daytime stomata of leaves are open, and exchanges of gases take place. Plants absorb carbon dioxide during the day to perform photosynthesis and release oxygen. Therefore, the atmosphere near a tree is good and fresh during the daytime. During the night, stomata are closed, and no such activity takes place; instead, some plants release toxic gases. So, sleeping under a tree during the day is better than sleeping under a tree during the night.