Exemption - ltcg

An assessee sold his flat in the FY 2014-15 and got LTCG of 45L. Let us say property 'A'

Now he purchased another property which he wants to sell it off in few months time. This is an under-construction property. Let us say property 'B'

Thereafter, from the amount received from sales, he wants to purchase another property within the same FY 2014-15. Let us say property 'C'.

What details he needs to put in the ITR for the FY 2014-15? Can he show only the 'C' purchase in ITR and claim exemption u/s 54? Or will he incur STCG also by selling the 'B' property within the same FY?

Thanks