Astudent viewing a cell with a microscop observes a cell wall, a cell membrane, and a nucleus. the presence of these structures indicates that the student is looking at a a (1) rabbit (3) worm (2) carrot (4) fly

2. Carrot

Explanation:

A plant cell typically comprises of an outer envelop which covers the cell is called as cell wall. The cell wall gives the cell it's shape. The cell wall covers the cell membrane which is selectively permeable for substances coming from the surrounding of the cells and allows some materials out of the cell. A typical plant cell also posses membrane bound nucleus and other cell organelles.

On the basis of the above explanation, carrot is the correct option. As it is a product of plant.

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.