In nuclear reaction `._2He^4 ._zX^A rarr._(z + 2) Y^(A + 3) + A`, denotes.

Options

A. Electron
B. Positron
C. Proton
D. Neutron

Explanation

To solve the nuclear reaction problem given, we need to apply the principles of charge and mass conservation. Let's break it down step by step.

### Step 1: Write down the nuclear reaction
The nuclear reaction is given as:
\[ _2He^4 + _zX^A \rightarrow _{z+2}Y^{A+3} + A \]

### Step 2: Apply charge conservation
In nuclear reactions, the total charge before the reaction must equal the total charge after the reaction.

- The charge of \( _2He^4 \) is +2 (since it has 2 protons).
- The charge of \( _zX^A \) is \( z \).
- The charge of \( _{z+2}Y^{A+3} \) is \( z + 2 \).
- The charge of \( A \) is 0 (since it is a neutron).

Setting up the equation for charge conservation:
\[ 2 + z = (z + 2) + 0 \]
This simplifies to:
\[ 2 + z = z + 2 \]
This equation is balanced, confirming charge conservation.

### Step 3: Apply mass conservation
Next, we apply mass conservation. The total mass number before the reaction must equal the total mass number after the reaction.

- The mass number of \( _2He^4 \) is 4.
- The mass number of \( _zX^A \) is \( A \).
- The mass number of \( _{z+2}Y^{A+3} \) is \( A + 3 \).
- The mass number of \( A \) is 1 (as it represents a neutron).

Setting up the equation for mass conservation:
\[ 4 + A = (A + 3) + 1 \]
This simplifies to:
\[ 4 + A = A + 4 \]
This equation is also balanced, confirming mass conservation.

### Step 4: Solve for A
From the mass conservation equation, we can see that:
\[ 4 + A = A + 4 \]
This means that the mass number \( A \) does not affect the balance, and we can conclude that \( A \) must represent a neutron, which has a mass number of 1.

### Conclusion
Thus, \( A \) represents a neutron, and the correct interpretation of the nuclear reaction is that \( A \) is indeed 1.