Bats frogs crocodiles and dogs all have a bone called humerus in their forelimbs. what does this suggest about their ancestry

Would really appreciate it, i have an idea but not completely sure

Before the can be observed by using a transmission electron microscope, cells are sliced into very thin sections. what disadvantage does this procedure present in the study of cellular parts

What is an endocrine function? (apex) a. esophageal glands release mucus into the esophagus b. salivary glands release saliva into mouth c. swear glands release sweat to the skin d. the pineal gland releases melatonin into the bloodstream