3-PGA is the first step stable product in ...(i) ..and is formed when initial CO.. acceptor ....(iii) ... take CO.. in presence of enzyme RuBisCO.

Options

A. (i) carbon -reduction cycle, (ii) PEP
B. (i) Calvin cycle , (ii) RuBP
C. (i) Calvin cycle , (ii) Malic acid
D. (i) Hatch and slack cycle , (ii) PEP

Answer

To solve the question step by step, we can break it down as follows:

### Step 1: Identify the Process
The question asks about the first stable product formed in a specific cycle when CO2 is fixed. The process being referred to is known as the Calvin Cycle.

**Hint:** Think about the primary function of the Calvin Cycle in photosynthesis.

### Step 2: Identify the First Stable Product
In the Calvin Cycle, the first stable product formed after the fixation of CO2 is 3-phosphoglycerate (3-PGA).

**Hint:** Recall the products formed during the Calvin Cycle and their order.

### Step 3: Identify the Initial CO2 Acceptor
The initial CO2 acceptor in the Calvin Cycle is ribulose 1,5-bisphosphate (RUBP). This molecule reacts with CO2 in the presence of the enzyme RuBisCO.

**Hint:** Remember the key molecules involved in the Calvin Cycle and their roles.

### Step 4: Identify the Enzyme
The enzyme that facilitates the reaction between CO2 and RUBP to form 3-PGA is called RuBisCO (ribulose 1,5-bisphosphate carboxylase/oxygenase).

**Hint:** Think about the enzymes that play a crucial role in carbon fixation.

### Final Answer
Putting it all together, we can fill in the blanks:
3-PGA is the first stable product in **(i) Calvin Cycle** and is formed when the initial CO2 acceptor **(ii) RUBP** takes CO2 in the presence of the enzyme **(iii) RuBisCO**.

### Summary of Steps
1. Identify the process (Calvin Cycle).
2. Identify the first stable product (3-PGA).
3. Identify the initial CO2 acceptor (RUBP).
4. Identify the enzyme (RuBisCO).