Molecules of phosphorus and ammonia are respectively:

Options

A. monoatomic and triatomic
B. monoatomic and diatomic
C. tetratomic and triatomic
D. tetratomic and tetratomic.

Explanation

To determine the molecular composition of phosphorus and ammonia, we need to analyze the number of atoms present in each molecule.

### Step 1: Analyze the molecule of phosphorus
- Phosphorus exists as \( P_4 \).
- This means that one molecule of phosphorus contains 4 phosphorus atoms.

**Conclusion for phosphorus:**
- Since there are 4 atoms in a molecule of phosphorus, it is classified as **tetraatomic**.

### Step 2: Analyze the molecule of ammonia
- The chemical formula for ammonia is \( NH_3 \).
- This indicates that one molecule of ammonia consists of 1 nitrogen atom and 3 hydrogen atoms.

**Calculation for ammonia:**
- Total number of atoms in ammonia = 1 (from nitrogen) + 3 (from hydrogen) = 4 atoms.

**Conclusion for ammonia:**
- Since there are also 4 atoms in a molecule of ammonia, it is also classified as **tetraatomic**.

### Final Conclusion:
Both phosphorus and ammonia are tetraatomic molecules.

### Answer:
The molecules of phosphorus and ammonia are respectively **tetraatomic**.

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