曹老师您好！

这是新概念3-33课，有一些疑问请教您：

We have all experienced days when everything goes wrong. A day may begin well enough, but suddenly everything seems to get out of control. What invariably happens is that a great number of things choose to go wrong at precisely the same moment.

It is as if a single unimportant event set up a chain of reactions.

1)这个It is as if... 是什么句型？只见过It looks as if等句型。还有我感觉这里的It是指代的前面的一句话，可是又有人说这里的It是虚指没意义？

Let us suppose that you are preparing a meal and keeping an eye on the baby at the same time.

2)为什么是a meal, the baby ? 为什么一个是不定冠词，一个是定冠词呢？很奇怪。

The telephone rings and this marks the prelude to an unforeseen series of catastrophes. While you are on the phone, the baby pulls the tablecloth off the table, smashing half your best crockery and cutting himself in the process. You hang up hurriedly and attend to baby, crockery, etc. Meanwhile, the meal gets burnt.

3) 前面假设一个场景(you are preparing a meal and keeping)，然后突然接下来所有的动词都用了“一般现在时”描述，这是为什么呢？下一段叙述了过去发生的事情，使用了一般过去时可以理解。还有为什么是attend to baby？没有the吗？

As if this were not enough to reduce you to tears, your husband arrives, unexpectedly bringing three guests to dinner.

4)为什么As if可以位于句首直接引导句子？As if前为什么没有主句呢？

Things can go wrong on a big scale, as a number of people recently discovered in Parramatta, a suburb of Sydney. During the rush hour one evening two cars collided and both drivers began to argue. The woman immediately behind the two cars happened to be a learner. She suddenly got into a panic and stopped her car. This made the driver following her brake hard. His wife was sitting beside him holding a large cake. As she was thrown forward, the cake went right through the windscreen and landed on the road. Seeing a cake flying through the air, a lorry driver who was drawing up alongside the car, pulled up all of a sudden. The lorry was loaded with empty beer bottles and hundreds of them slid off the back of the vehicle and on to the road. This led to yet another angry argument. Meanwhile, the traffic piled up behind. It took the police nearly an hour to get the traffic on the move again. In the meantime, the lorry driver had to sweep up hundreds of broken bottles. Only two stray dogs benefited from all this confusion, for they greedily devoured what was left of the cake. It was just one of those days!

5) what was left of the cake = the thing that was left of the cake =  the thing that of the cake was left: that of 怎么理解呢？It是指代前面刚刚发生的不顺心的事，those 是指平常发生过的很多不顺心的所有事情，it是其中之一？

麻烦曹老师帮助分析，谢谢！