False there may be two or more dependent variables in a well designed experiment
The answer is an envelope.
A virus is an infectious agent that can replicate only inside a host cell. When it is outside the cell, it consists of genetic material coated with protein capsid. Some viruses also have an envelope which covers capsid. The function of the envelope is to identify and bind some receptor sites on the host membranes. After fusing with the cell membrane, it allows to capsid and genetic material to enter the cell and infect it.
If the underlined verb is <em>will have been talking, </em>in the sentence Lillian will have been talking for two hours by the time she finishes her classical music lecture, then the correct answer is D. future perfect progressive.
A would be - will talk.
B would be - will have talked.
C would be - will be talking.
C.) Food moves up from roots
I think the answer is C, but it is hard to tell because it seems incomplete.
