The value of one microcurie $=$ $.......$ disintegrations / second

Tritium undergoes radioactive decay giving

What kind of radioactive decay does not lead to the formation of a daughter nucleus that is an isobar of the parent nucleus?

If by mistake some radioactive substance gets inside the human body,then from the point of view of radiation damage,the most harmful will be the one which emits

Radioactivity was discovered by

Of the following radiations,the one most easily stopped by air is