Someone has told me that if the verb of principal clause is continuous, then the subordinate clause started with
while must also be in continuous tense. For example,
While mobile phone is becoming increasingly popular, the rate of terrorism is rising rapidly.
But in a grammar book, I saw the following sentence:
The rich are building heavy complexes, while the poor are homeless.
Here the principal clause is present continuous tense, but the subordinate clause is not also present continuous tense rather it is present indefinite tense.
If the mentioned rule by someone is wrong and the 2nd sentence is correct, then can I rewrite 1st sentence as following???
The rate of terrorism is rising rapidly, while mobile phone becomes popular.