Ringing/girdling experiments demonstrate
(a) Phloem is responsible for the translocation of food
(b) Xylem is responsible for the ascent of sap
(c) Transpiration pull
(d) Both (a) and (b)

Hint: The ringing experiment also known as the Girdling experiment was conducted to explain the pathway of translocation of organic nutrients and also to identify the tissue involved in it. It is a strategy in which outer tissues or bark of a stem is detached, leaving only xylem and pith unharmed.

Complete answer:
The ringing/girdling experiment demonstrates that Phloem is responsible for the translocation of food as well as no effect on water transport shows that xylem is responsible for the ascent of sap. The experiment was conducted by Malpighi.
In this experiment following steps are involved:
- On the trunk of the tree, a ring of bark up to a depth of the phloem layer is carefully removed.
- This narrow ring of bark consists of a phloem, cortex, and cork.
- After a few weeks, the bark above the ring on the stem swells.
The leaves do not wilt but growth below the ring was reduced.
- This swelling of bark above the ring was due to the accumulation of nutrients in that region as the translocation of sugars and other materials down the plant was stopped whereas the upward movement of water was not affected.

So, the correct answer is ‘Both (a) and (b)’.

Note: This experiment proves that phloem is the tissue responsible for the translocation of food in one direction, i.e., towards the roots. On the other hand, no effect on water transport shows that xylem is responsible for the ascent of sap. The xylem and phloem are thus also called conducting tissues of vascular tissues.