Answer:
bombarding it with an energetic particle
Explanation: nuclear reaction, a change in the identity or characteristics of an atomic nucleus, induced by bombarding it with an energetic particle. The bombarding particle may be an alpha particle, a gamma-ray photon, a neutron, a proton, or a heavy-ion.
Answer : The
must be administered.
Solution :
As we are given that a vial containing radioactive selenium-75 has an activity of
.
As, 3.0 mCi radioactive selenium-75 present in 1 ml
So, 2.6 mCi radioactive selenium-75 present in 
Conversion :

Therefore, the
must be administered.
C. Ca and Br because they're metals and nonmetals
Observation : a piece of info we all gather through our 5 senses
Hypotheses: a testable explanation for an observation
Data: info that scientists gather during an experiment
Experiment: a procedure that is designed to test a hypothesis
Conclusion a judgment or decision
Scientific method a series of steps
Models help us better understand the phenomena