Answer:
a
Explanation:
its a semi permeable membrane. it chooses what can go in and out so nothing bad happens.
500 million for the first picture and for the text i guess it evolved physical reproductive body cells and parts that makes sexual reproduction change as itself as well as birth due to not only human nature but man made things as well, example: hospitals, medicine, chemicals, etc.
Answer:
False
Explanation:
A virus (which is a pathogen) has a lot of antigens on its surface, so they can't be used interchangeably.
