What happens to the mass of substances during a chemical reaction? a mass is lost. b mass is gained. c mass is not gained or lost. d mass is both gained and lost.

its (d) i know that for a fact because i am smart? i am a fifth grader 1

answer; i believe that the correct answer is (southeast

answer; i believe the correct answer is (a) nigeria is the largest african crude (oil) supplier; /// so revenue from petroleum;