What is the appropriate action for the nurse to take?

A is the best answer to this question. When there is a residual amount that is more than 100 ml, this is already a sign that the feeding should immediately be stopped. Due to this rule, the other options are already incorrect. The residual amount is 150 ml which means that there are other things that the nurse can do in order to figure out the larger than usual residual.

Take note that the feeding is not stopped unless there are some weird contents that show some abnormalities in its characteristics and/or color. The nasogastric tube is meant to provide people with their food and medicine straight to the stomach.