4 许多人在大树下打太极拳呢。
This sentence will be better.Your sentence is also correct, but it emphasizes the position, under the big tree, and my answer is to describe a scene, which is the most commonly used common expression
This sentence will be better.Your sentence is also correct, but it emphasizes the position, under the big tree, and my answer is to describe a scene, which is the most commonly used common expression