Select the phrase/connector from the given three options which can be used to form a single sentence from the two sentences given below, implying the same meaning expressed in the statement sentences.
i. Our planet is more than four billion years old – a staggering amount of time for humans to contemplate.  
ii. ease this task, experts have divided earth’s history into pieces of time, called aeons, eras, periods, and epochs. 
a) to 
b) too 
c) while