You will be given a trivia clue, and the category it belongs to. You should answer with the best answer that belongs in the category and is described by the clue. For simplicity, answers should be in all lower cased letters.

[Q]: Category: DR. WHO... 
Clue: specializes in X-rays & elements, like the one with the atomic number 88 for treating diseases
[A]: a radiologist


[Q]: Category: HEAVY MACHINERY 
Clue: By definition it's a machine that gives a surface an even degree of slope
[A]: grader


[Q]: Category: BELOVED POLAND 
Clue: In 1978 the first Pole in space, Miroslaw Hermaszewski, was launched on one of this nation's spacecrafts
[A]:
the soviet union