Understanding Rational Numbers

A rational number is any number that can be expressed as a fraction '$p/q$', where '$p$' and '$q$' are integers and the denominator '$q$' is not zero. Let's analyze the given options:

• Option 1: $\sqrt{3}$ - The square root of 3 is an irrational number because it cannot be written as a simple fraction of two integers.
• Option 2: $4 - 6i$ - This is a complex number, involving the imaginary unit '$i$'. It is not a real number, hence not rational.
• Option 3: 2 - This is an integer. Any integer '$n$' can be written as '$n/1$' (e.g., $2 = 2/1$). Therefore, 2 is a rational number.
• Option 4: $7i$ - This is a purely imaginary number, a type of complex number. It is not a real number, hence not rational.

Based on the definition, the number 2 is the only rational number among the choices.