Hurry: which describes why radioisotopes can be used as tracers in studying the biological and chemical processes of plants?
the radioisotope is chemically identical to the nonradioisotope the plant normally uses
the radioisotope is absorbed more quickly than the nonradioisotope the plant normally uses,
the radioisotope converts the nonradioisotope normally used by a plant into a radioisotope.
the radioisotope travels through the plant without participating in any chemical processes

Cyclotrons are widely used in nuclear medicine for producing short-lived radioactive isotopes. these cyclotrons typically accelerate h- (the hydride ion, which has one proton and two electrons) to an energy of 5 mev to 20 mev. this ion has a mass very close to that of a proton because the electron mass is negligible—about 1 2000 of the proton’s mass. a typical magnetic field in such cyclotrons is 1.9 t. (a) what is the speed of a 5.0-mev h-? (b) if the h- has energy 5.0 mev and b = 1.9 t, what is the radius of this ion’s circular orbit?