what nuclear fission and nuclear fusion have in common? A. They’re both used in power plants B. they have less mass than their reactants C. they start with the same reactants D. their products have more mass than their reactants

A. They’re both used in power plants . . . No.  

Nuclear fission is used in all nuclear power plants.  Fusion isn't used in any power plants yet, because we can't control it safely enough yet.  The only thing we can use nuclear fusion for is still bombs.

B. they have less mass than their reactants . . . No.  

Fission involves breaking atoms into pieces. Its products have less mass than its raw materials.  Fusion involves sticking atoms together to make new ones.  Its products have more mass than its raw materials.  Whatever the incomplete statement ' B ' is trying to say, it's not true of both processes.

B. ==> If you try really hard, this statement (B) can be undertood as true.  The TOTAL MASS after both a fission reaction and a fusion reaction is less than the total mass of whatever was fissled or fuzled.  In both cases, the missing mass is accounted for by the energy that was radiated from the site of the nuclear reaction.

But the statement in ' B ' is very poorly written.  When you read it, you don't know what 'they' refers to.  

C. they start with the same reactants . . . No.  

Man-made fission starts with the heaviest atoms ... Uranium and Plutonium.  Man-made fusion starts with the lightest atoms ... Hydrogen.

D. their products have more mass than their reactants ... No.

Fission breaks heavy atoms and makes lighter ones.  Fusion glues light atoms and makes heavier ones.

Gee whiz !  None of the choices is correct.

15.3 cos 65 degrees trig

the duration of a photographic flash is related to an rc time constant, which is 0.100 μs for a certain camera.