The future seen from the past

Hello, I’d be grateful if you would help me with the following.

Choose the most appropriate option to complete these sentences.

1. The meeting was to have taken place in the hall.
   1. but had to be cancelled at the last minute.
   2. and was well attended.

2 The bridge was to have been completed this year,

A but a number of accidents have led to delays.

B and is to opened by the president next month.

3 Later, in Rome, I was to meet Professor Pearce,

1. and was very impressed by his knowledge of Italian culture.
2. but he left before I got there

.4 After the war, he was to teach at London University,

A but no money was available to employ him

B for ten years.

Answers:

• A
• A
• A
• B

(Source: Cambridge Advanced Grammar)

I cannot figure out why these options were chosen over the other options.

The only things I can gleam from the answers are that numbers 1A and 2A

are like conditions that were not met, and numbers 3A and 4B were facts

which directly resulted from the decision in the past, about the future.

Unfortunately, using the same logic, i.e. the effects of the earlier decision,

And the unmet conditions, I get the following answers.

1 B

2 B

3 B

4 A

Or, does it have something to do with predictions and plans?

At the point in the past when the decisions were made,

would it be possible to alter the clauses slightly?

So, 1 B would read; and will be well attended.

2 B would not have to be changed.

3 B would read; but he will leave before I get there.

4 A would read; but no money will be available to employ him.

Apologies if this seems complicated.

Many thanks,