Hey there!
A function is a relation to numbers in which an input value as a specific output value.
a) Is a function. All x values go to specific y values. For domain, look at the x values. You go from 2 to 8. So, 2≤x≤8 (we can assume the line just goes this long since we are not given anymore information) For the range, we have the same thing. It goes from 5 to 8. 5≤y≤8
b) Is not a function. 1 cannot go to two y-values.
c) Is not a function. Does not pass vertical line test.
d) Is a function. Passes the vertical line test. For the domain on this one, it would be infinite, which you could represent as (-∞,∞) It is infinite because the line as two arrows that continue forever. For the range, it would be anything greater than 2. y≥2 or 2≤y
The question stated you only needed to find the domain and range for the functions, so you would just do it for a) and d).
I hope this helps!
~kaikers