Explanation:
the domain of a function is always the interval or set of all valid input values (usually x, but here t).
the range is the interval or set of all valid result values (usually y or f(x), here h(t)).
as the graph shows, the function works only for values of t starting at 0 (at 0 seconds the object has 0 ft height, it is still on the ground and about to launch).
and it ends at t = 7.
obviously the object hits the ground after 7 seconds again after coming back down. so, the height function does not make any sense for values of t after that.
so, again, the domain is
0 <= t <= 7