Answer:
Part A B. Part B C.
Explanation:
A) The elementary charge e (without sign) is equal to the charge of one electron (with negative sign) or to the charge of one proton (with positive sign), so the proton must have a total charge of +e.
if u = +2/3 e and d= -1/3 e, we need a combination which sum gives +3/3 e.
Combination A adds to 6/3e, so it is not possible. C adds to zero, and D gives a negative result.
The only remaining choice is udd:
uud ⇒ +2/3 e + 2/3 e -1/3 e = +3/3 e = +e
So, the statement B is true.
B) As the neutron has no net charge, we need to find a combination which sum adds to zero.
So, A and D are not possible, as they are combinations of the same type of quarks, so the sum is either positive or negative, but not zero.
uud gives +e (we chose it to make a proton in part A), so the only remaining choice is udd:
udd⇒ +2/3 e -1/3 e - 1/3 e = 0
So the statement C is true.
