Capacitances of 10uf and 20uf are connected in parallel,
andthis pair is then connected in series with a 30-uf capacitor.
what is the equivalent capacitance of this arrangement?

The equivalent capacitance will be  

Explanation:

We have given two capacitance

They are connected in parallel

So equivalent capacitance

This equivalent capacitance is now connected in series with

In series combination of capacitors the equivalent capacitance is given by

So the equivalent capacitance will be  

come closer and become far apart and become steam/gas

the answer is a. hope this .