Question

read the paragraph about the function of the appendix. select the sentence that should be removed to improve the focus of the paragraph. the appendix is a small sac attached to the large intestine, and for many years, most medical experts believed that it had no real function in the human body. for a long time, most doctors believed the appendix was essentially useless. more recently, however, research has begun to suggest that the organ may play a role in the early development of the human endocrine system, which secretes important hormones into the bloodstream. scientists also believe the appendix may help people maintain a healthy immune system. these researchers believe the appendix may provide a space for white blood cells to interact with harmful antigens, creating helpful antibodies in the process. in addition, the appendix may also hold an emergency supply of helpful bacteria, which can be used to repopulate the guts microbiome after an illness.

Explanation:

The paragraph focuses on the function of the appendix. The sentence "For a long time, most doctors believed the appendix was essentially useless" repeats the idea from the previous sentence ("most medical experts believed that it had no real function") and doesn't contribute new information about its function. Other sentences discuss potential functions (endocrine system, immune system, bacteria supply).

Answer:

For a long time, most doctors believed the appendix was essentially useless.