Match List - I with List - II.

	List-I		List-II
(a)	S phase	(i)	Proteins are synthesized
(b)	G2 phase	(ii)	Inactive phase
(c)	Quiescent stage	(iii)	Interval between mitosis and initiation of DNA replication
(d)	G1 phase	(iv)	DNA replication

To determine the correct matching between the cell cycle stages in List-I and their key characteristics in List-II, let us analyze each term step-by-step:

1. S phase (Synthesis Phase):
During the S phase of interphase, the amount of DNA per cell doubles. This is the stage where active DNA replication takes place. Therefore, (a) matches with (iv) (DNA replication).

2. G₂ phase (Gap 2 Phase):
In the G₂ phase, the cell continues to grow and prepares for mitosis by synthesizing necessary proteins, such as tubulin, which are required for spindle fiber formation. Therefore, (b) matches with (i) (Proteins are synthesized).

3. Quiescent stage (G₀ phase):
Some cells in adult animals do not appear to exhibit division (e.g., heart cells) or divide only occasionally. These cells exit the G₁ phase to enter an inactive stage called the quiescent stage (G₀ phase) of the cell cycle. Cells in this stage remain metabolically active but no longer proliferate unless called on to do so. Therefore, (c) matches with (ii) (Inactive phase).

4. G₁ phase (Gap 1 Phase):
The G₁ phase corresponds to the interval between mitosis (M phase) and the initiation of DNA replication. During this phase, the cell is metabolically active and continuously grows but does not replicate its DNA yet. Therefore, (d) matches with (iii) (Interval between mitosis and initiation of DNA replication).

Matching the phases accordingly, we get:
(a) - (iv)
(b) - (i)
(c) - (ii)
(d) - (iii)

Thus, the correct option is (a) - (iv) , (b) - (i) , (c) - (ii), (d) - (iii).