A, B, C, or D? Please help!

I'm not sure of this question, yet i know you may get angry but, just know your loved and if going through a hard time i'm so so sorry, i know how it feels it sucks. take care of yourself, drink water, listen to that one song that makes you dance in your room and go do what YOU love. your beautiful your perfect and dont listen to what anyone says. i love u, everyone loves u, i know its scary but it happens to everyone life isnt a peice of cake unfortunatly and it sucks but woahh your strong! if you need someone to talk to leave a comment below, happy hoildays everyone!

P.S, im looking into the answer of this question. I may not answer it right on time (since i'm not the smartest...) but i promise ill try my best! Also, i am not doing this for points im doing this to make others smile. I hate how no one checks up on anyone, lots of people are going through a stressful time (including me) and i just want to let everyone know that its okay not to be okay! I hope that you all find happiness in every possible situation, once again  HAPPY HOLIDAYS! Also, good luck. Please dont stress it!

the real answer is b. scintillation counter