过去时。使用动词的过去时态。
before是介词，在一般情况下加动名词，也就是ing形式。但也不可一概而论，视情况而定。
2.如since如果解释为“自从.以来”，引导时间状语从句时，则其前面的主句用现在完成时。
3.其后如果是从句则用一般过去时，引导时间状语（从句）时：其后的从句用一般过去时(其前面的主句用现在完成时。
一. 基本概念
时态(tense)是一种动词形式，不同的时态用以表示不同的时间与方式。它是表示行为、动作、状态在各种时间条件下的动词形式，在英语中有16种时态。
二. 种类
所谓"时"就是行为发生的时段或状态存在的时段，有完成状态、进行状态、完成进行状态或一般状态四种。由时和态结合，便形成下列十六种时态:
一般现在时，一般过去时，一般将来时，一般过去将来时;
现在进行时，过去进行时，将来进行时，过去将来进行时;
现在完成时，过去完成时，将来完成时，过去将来完成时;
现在完成进行时，过去完成进行时，将来完成进行时，过去将来完成进行时。
三. 转换
一般过去时与现在完成时的转换:
A. He joined the League o years ago.
B. He has been in the League for o years.
C. It is o years since he joined the League.
D. Two years has passed since he joined the League.
2.一般现在时与现在进行时的转换：
Peter is at work，but Mike is at play.Peter is working，but Mike is playing.
3.现在进行时与一般将来时的转换请看:
The train is leaving soon.The train will leave soon.
什么时态都可以.
1.It is said that God is almighty.
据说上帝是万能的.收藏指正
2.It is said that acupuncture is painless.
据说针灸没有疼痛感觉.收藏指正
3.It is said that his child is lost.
据说他的孩子不见了.收藏指正
4.It is said that she is a siren.
据说她是个妖艳女人.收藏指正
5.It is said that the universe is infinite.
据说宇宙是无限的.收藏指正
6.It is said that he is a millionaire.
据说他是一个百万富翁.收藏指正
7.It is said that the country is in anarchy.
据说那个国家处于无 *** 状态.收藏指正
8.It is said that this island is iron ore .
据说这个岛盛产铁矿石.收藏指正
9.It is said that she is sweet and enty.
据说她姿容秀美,年方20.收藏指正
10.It is said that the sea is sweat originally.
传说海水最初是甜的.收藏指正
11.It is said that civilization is always on the move.
有人说文明总是在进步.收藏指正
12.It is said that he is a master of intrigue.
据说他是搞阴谋诡计的老手.收藏指正
13.It is said that wisdom is born with a man.
有人说智慧是与生俱来的.收藏指正
14.It is said that it begins at 00 p.m.
听说是下午两点开始.收藏指正
15.It is said that Jenny is in love with Tom.
据说詹妮正在和汤姆恋爱.收藏指正
16.It is said that three prisoners crashed out yesterday.
据说昨天有三个囚犯越狱.收藏指正
17.They say [It is said that] he's a miser.
据说他是一个小气鬼.收藏指正
18.It is said that the squall will e tomorrow.
据说暴风雪明天就要来了.收藏指正
19.It is said that his lameness resulted from an aident .
据说,他腿瘸了是一次事故造成的.收藏指正
20.It is said that there are wolves in this forest
据说这片森林里有狼.
过去式
--------------精锐教育老师很高兴为您解答。
你提问的方式错了吧,,,about doing
about
英 [ə'baʊt]
美 [ə'baʊt]
prep. 关于；大约
n. 大致；粗枝大叶；不拘小节的人
adj. 在附近的；四处走动的；在起作用的
adv. 大约；周围；到处
n. (About)人名；(法)阿布
更多释义>>
[网路短语]
About 关于我们,关于,大约
e about 发生,产生,出现
talk about 谈论,议论,谈到
remember to do 是不要忘记做... (不定式）
remember doing 是记得曾经做过的事情 (动名词)
例子：
Please remember to bring the dictionary. 请记得（不要忘记）带上字典。
I remember seeing him last year.
我还记得去年见过他。
加原形to
加原形也可