Cell theory was given by :

The correct option is A

Schleiden and Schwann

The correct option is A.

Explanation of the correct option :

1. The Cell Theory was first given by M.J Schleiden and Theodor Schwann in 1839.
2. It states that all the living beings whether plants or animals are composed of cells that are from pre-existing cells.
3. However, they failed to explain how new cells are formed.
4. Rudolf Virchow(1885) modified the cell theory and concluded that new cells develop from the division of pre-existing cells.

Explanation of the incorrect option:

Option B:

1. Robert Hooke was the first one who introduced the cell in the year 1665.
2. While working on the cork, he saw small compartments structured like honeycombs and named them cells.

Option C:

Rudolf Virchow in 1885 was the one who modified the cell theory and concluded that new cells develop from the division of pre-existing cells.

Option D

1. Ernst Haeckel proposed the Biogenetic Law.
2. Haeckel studied the evolution thoroughly and claimed that phylogenies (the process by which groups of organisms diversify from one another) influenced the development of embryos (ontogeny) .

Final answer: Cell theory was given by Schleiden and Schwann.