The half-life of a radioisotope is the amount of time it takes for a. half the sample to decay. b. all the sample to decay. c. the age of an artifact to be calculated. d. detectable radiation to be absorbed by a sample.

C the age of an artifact to be calculated

Aphysical change is one that you can put in and remove like a ham sandwich. the stuff you put in there can be changem its not permanet. a chemical change is on that can't be change thats permanet. like when you make a cake and bake it. you can't get those ingredients back.

True is ur answer : )