恳请答复, 谢谢. 关于 sometimes and some 的理解

Note: both questions are from CXD.

1

If athletes want better performances, they should train at high altitudes. At higher altitudes, the body has more red blood cells per unit volume of blood than at sea level. The red blood cells transport oxygen, which will improve performance if available in greater amounts. The blood of an athlete who trains at high altitudes will transport more oxygen per unit volume of blood, improving the athlete’s performance.

Which of the following, if true, would be most damaging to the argument above, provided that the athlete’s heart rate is the same at high and low altitude?

(A)  Scientists have found that an athlete’s heart requires a period of time to adjust to working at high altitudes.

(B)   Scientists have found that the body’s total volume of blood declines by as much as 25 percent at high altitudes.

(C)  Middle-distance runners who train at high altitudes sometimes lose to middle-distance runners who train at sea level.

(D)  The performance of athletes in competitions at all altitudes have improved markedly during the past twenty years

       (E)At altitudes above 5,500 feet, middle-distance runners often better their sea-level  running times by several second.

The correct answer is B.

C is not correct is because the use of "sometimes" in the sentence. (According to the explanation provided by the book)

My understanding: "sometimes" can not represent the "all the time" in general, so it is not correct.

2

It is important to teach students to use computers effectively. Therefore, students should be taught computer programming in school.

Which of the following, if true, most weakens the argument above?

(A)  Only people who use computers effectively are skilled at computer programming.

(B)   Only people skilled at computer programming use computer effectively.

(C)  Some people who use computers effectively cannot write computer programs.

(D)  Some schools teach computer programming more effectively than others.

(E)   Most people who are able to program computers use computers effectively.

C is the correct answer.

But here, "some" people means "some people", can't not represent the genera population either. But the use of "some " in C doesn't make the answer incorrect.

I am not sure how much similarity the above two questions share, but this question just popped into my head when I read the explanations from the book. Probably I didn't state the question very well either, but still hope get answers here.

thank you very much!!