過去進行式~

1.過去進行式可不可能+現在進行式時態e.g
at the moment,now.....
因為at the moment,now.....呢d係講緊現在,係指在現時的時刻,當然係配合present continuous tense。你用過去進行式,話明係過去左,仲點會係有依家既意思呢??但如果用at that moment就ok,因為係講緊係個個時刻,咁就可以指past.
例子:
a.The car is coming now !!!
b. I was doing my homework when you called me .
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2.
首先你要知道呢d時式既用法:
現在進行式---表示現在進行中或有將會去做的意思
e.g.I am going to the school this Sunday.
現在式---用於現在或一些事實
e.g. The sun rises in the East.
至於你話如果文章開始是過去式，以後可不可以是現在進行式,現在式?

咁就要睇你究竟係用轉述句定直述句。直述句即係一d對話就可以用現在進行式,現在式,因為對於佢地個d野係屬於現在,
如:Mary says," I am having a fun day today."
但如果用轉述句,即reported speech ,就要轉做past continuous
即
present tense→past tense
present continuous tense→past continuous tense
present perfect tense→past perfect tense....

Mary said she was having a fun day at that day.
但如果係講緊一d廣為人知既事實,定理,規律等,無論用轉述句定直述句,都係用present tense.