4. Celery stalks that are immersed in fresh water for several hours become stiff. Similar stalks left in a 0.15 M salt solution become limp. From this we can deduce that the fresh water ___________.(A)and the salt solution are both hypertonic to the cells of the celery stalks (B)is hypotonic and the salt solution is hypertonic to the cells of the celery stalks (C) is hypertonic and the salt solution is hypotonic to the cells of the celery stalks (D) is isotonic and the salt solution is hypertonic to the cells of the celery stalks