Q1: When matching polarity connections have been made and the potential difference (PD) is above 0.7 V, the diode is considered to be:

ANS:B - forward biased

This is in response to WALEED and AMIT. It is true that the BARRIER potential (natural difference of potential between the p-type and the n-type sides of the junction) of Si is approximately 0.7V and that of Ge is approximately 0.3V.

Now, here we are talking about the TERMINAL potential (potentially applied to a p-n junction to obtain a desired mode of operation) which must be above the barrier potential (0.7) in order for the current to flow across the junction since the polarities are matched ie positive linked to the positive terminal.