Assertion: Cell theory was put forward by Schleiden and Schwann.
Reason: It is applicable to all cells including viruses.
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.
B. Both Assertion and Reason are correct and Reason is not the correct explanation for Assertion.
C. Assertion is correct but reason is incorrect.
D. Both Assertion and reason are incorrect.

Hint: The cell was first discovered by Robert Hooke. Cell theory says those living organisms are made up of cells. The cells are the basic structural unit of life and also the basic unit of reproduction.

Complete Answer:
To solve this question, we must know about cell theory and its application over viruses.
Cell theory was given by Schleiden and Schwann.
According to cell theory-
- Living organisms are composed of one or more cells.
- Cells are the basic unit of structure and organism.
- Cells exist from pre-existing cells.
- The cell is composed of a definite nucleus and other organelles which is surrounded by a definite membrane.
- The cell theory is applicable to all living cells but this theory does not hold good for viruses. - The viruses are nonliving crystal particles. They lack definite cell structure.

The correct answer is (C).

Note: A virus is a non-living being as they do not have a definite cell structure. They do not grow and do not have their own energy. A virus is composed of either DNA or RNA which is surrounded by a protein coat. Viruses do not replicate on their own. They require a host for replication. It kills the host in which it houses.