Celery stalks that are immersed in fresh water for several hours become stiff and hard. Similar stalks left in a 0.15 M salt solution become limp and soft. From this we can deduce that

A. the fresh water is isotonic and the salt solution is hypertonic to the cells of the celery stalks.

B. the fresh water is hypertonic and the salt solution is hypotonic to the cells of the celery stalks.

C. the fresh water and the salt solution are both hypotonic to the cells of the celery stalks.

D. the fresh water is hypotonic and the salt solution is hypertonic to the cells of the celery stalks.

E. the fresh water and the salt solution are both hypertonic to the cells of the celery stalks.

B. the fresh water is hypertonic and the salt solution is hypotonic to the cells of the celery stalks.

Explanation:

A hypertonic medium is precisely one that has a higher solute concentration than another medium. This, in turn, is hypotonic compared to the former. Thus, these classifications can only be employed in the sense of comparison and not as the primary definition of the osmotic characteristic of a solution.

When a cell is placed in a hypertonic solution, that cell tends to seek osmotic balance and absorbs some of the solution's solutes becoming rigid and hard. For this reason, we can say that fresh water is hypertonic in relation to celery stem cells.

On the other hand, when the solution is hypotonic, the cell trying to reach an osmotic equilibrium loses part of its solutes to the solution, becoming soft and flabby. For this reason, we can say that saline is hypotonic for celery stem cells.

I reckon, the correct option is option C, the fresh water and the salt solution are both hypotonic to the cells of the celery stalks.