What is the approximate percentage of criminal convictions which never reach a full trial but result from guilty pleas?A) 10% B)...

The correct answer to this question is E.  Something like
90% of all criminal cases end up in convictions without going to trial.  This process is
known as plea bargaining.  As the link below tells
us,

Although
plea bargaining is often criticized, more than 90 percent of criminal convictions come
from negotiated pleas. Thus, less than ten percent of criminal cases go to
trial.

This clearly shows
that E is the correct answer.

As the quote tells us, this
is fairly controversial.  The US Constitution guarantees people a trial by jury. 
However, if only about ten percent of cases actually go to trial, that right seems to be
denied.  Because of this, many critics of plea bargaining argue that plea bargains end
up with defendants being pressured to accept guilty pleas without the benefit of a
trial.