51.
Decay is an immutable factor of human life.

52.
Quite unabashed, he began his scholarly lecture on what was obvious to everyone.

53.
There is not a single word that is redundant in the report.

54.
This group is quite heterogeneous some are very rich while some are very poor.

55.
I don't see why he should be so obsequious to his brother just because the latter is rich.