tense question (appeared on tests)

[edison_chen_e_c]

What I've done wrong on the tests:
1.The weather in Taiwan______a lot in the past few years because the serious air pollution year after year.
(A)changed (B)has changed

I thought it was A, but the answer is B, I really can't understand.

2.I______for the doctor for half an hour last time.
(A)had waited (B)have waited (C)was waiting (D)waited

I thought it was A, but the answer is D, I don't know why.

[Mister Micawber]

.
1-- 'in the last few years' includes the time up to 'Now'; therefore, present perfect tense.
2-- The waiting was completed in the past and there is no reference to another past time; therefore, simple past tense.
.
_________________
Canadian-American native speaker
who teaches English for a living at Mister Micawber's
ESL cafe: Interview with Mr. Micawber

[edison_chen_e_c]

OK, Mr. MM.

[lost_soul]

Hi, Mister Micawber

I had waited for the doctor for half an hour last time but he didnt show up so I went home

Does it work?
_________________
Alex

I like exercise

[Mister Micawber]

Not by itself.
_________________
Canadian-American native speaker
who teaches English for a living at Mister Micawber's
ESL cafe: Interview with Mr. Micawber

[lost_soul]

[Mister Micawber]

.
Yes! That's fine, LS-- and if you put 'finally' before 'showed up', it would be even better.

As you know, the past perfect is less and less used nowadays (except among ESL/EFL students), and often appears overly formal. Its use is restricted to:

1-- Contexts with two past events occurring at different past times, and
......a-- their sequence is unclear and/or
......b-- emphasis of the precedence of the events is wanted.

(And can anyone tell me how to indent in a post?)
.
_________________
Canadian-American native speaker
who teaches English for a living at Mister Micawber's
ESL cafe: Interview with Mr. Micawber