A - one fourth of the teachers are from abroad
B- When I opened the beer, my friends showed up. In the sentence, the actions "opened" and "showed up" are short actions. According to grammar, when there's a short action right after another one, you use the past simple for both.
C- The man may be late, as happened yesterday. (gab).*
D- Bill has a lot of money.
E - Most of (the) people go with me.
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* The second clause is dependent on the first, which completes its meaning. the man might be late as he was yesterday. Adding the dummy pronoun 'it' changes the overall meaning of the sentence. it portends that the man may have been late due to something which took place the day before.