Directions:
In the following passage, some words have been deleted. Read the passage carefully and select the most appropriate option to fill in each blank.
Life processes are similar in all animals with (1)______. So physiologists can find out a lot about the human body by studying animals (2)______ frogs, rats, and rabbits. Sometimes, research involves the death of these animals. But, physiologists take great care to not (3)______ the animals. The animals are (4)______ put to sleep during the experiments. It is only by physiological research (5)______ medicine has been able to advance.
Select the most appropriate option to fill in blank number 4.