Tonsil is an organ found inside our throats wherein its main role in our body is to protect our airways from bacteria and viruses entering by trapping these pathogens. In addition, if that student would have her tonsils removed due to infection, she would most likely be unprotected against these pathogens due to the absence of tonsils.
The answer to this is The Females give birth to live young and their endoskeleton is made up of chitin.
The statement they breathe using gills isn't the right answer because that is part of fishes not a mammal and fishes lay eggs not live young.
The statement the females have mammary glands isn't right because only male mammals have that.
So your true statement is The females give birth to live young and their endoskeleton is made up of chitin.
Hope this helped :)
Have a great day