'Due to' v/s 'Because of'

Is this sentence correct?

The physical test was postponed due to the bad weather.

Even though this might sound correct to you it's actually incorrect; the correct sentence will read:

The physical test was postponed because of the bad weather.

Rule - On the GMAT 'due to' will NEVER be used to replace 'because of'; it can only replace 'caused by'.

Now, in the above sentence, if you were to replace 'because of' with 'caused by' the sentence will read:

The physical test was postponed caused by the bad weather.

This obviously does not make any sense, hence we cannot use 'due to' in this sentence.

However the following sentence makes sense:

The postponement of the physical test was caused by the bad weather.

In the above sentence since 'caused by' makes sense we can replace it with 'due to':

The postponement of the physical test was due to the bad weather.

To Sum it Up:

1. On the GMAT, 'due to' cannot be used to replace 'because of'
   
   
2. 'Due to' can only be used to replace 'caused by'