Option A:
{3, 4, 5, 6}
Solution:
In the given table X column have 3, 4, 5, 6 and Y column have 4, 4, 2, 5.
The domain is the set of all values for which the function is defined.
The domain of the function is set of all X values.
Option A: {3, 4, 5, 6}
Set of all X values {3, 4, 5, 6}.
It is correct.
Option B: (3, 4), (4, 4), (5, 2), (6, 5)
Here, the given values are ordered pairs of domain and co-domain.
It is not correct.
Option C: (3, 4)
Here, (3, 4) is a ordered pair of domain and co-domain.
It is not correct.
Option D: {2, 4, 5}
Here, {2, 4, 5} are values of co-domain.
It is not correct.
Hence {3, 4, 5, 6} is the domain of the function.