The domain is the set of values of the independent variable (usually called "x") for which the function (usually f(x)) is defined.
1) The function is defined by ordered pairs.
The values that the independent variable takes are: 3, 4, 6 and 8, so the domain is D = {3,4,6,8}.
This functions satisfy the domain asked.
2) The graph shows that the function is defined for x = 1,2,3,4.
This does not correspond to the domain D = {3,4,6,8}.
3) In this case the function is defined in oredered pairs.
As the function in 1) it has the same domain: D = {3,4,6,8}.
This functions satisfy the domain asked.
4) The table is defined for x = 3,6,8,9,10.
x=10 is not in the asked domain, so this function does not satisfy the domain asked.
5) This function in ordered pairs is defined for x=1,5,7,10, so it does not satisfy the domain asked.
6) The plotted function is defined for x=3,4,6,8, so it correspond to the domain asked D={3,4,6,8}.
Answer: Functions 1, 3 and 6.