In the following passage some of the words have been deleted. Read the passage carefully and select the correct answer for the given blank out of the four alternatives.

Deserts probably existed much (1) ______, during former periods of global arid climate in the lee of mountain ranges that sheltered them from (2) ______ or in the centre of extensive continental regions. However, this would have been primarily before the evolution of angiosperms which are (3) ______ as seed producing plants. Only a few primitive plants, which may have been (4) ______ of the ancient desert vegetation, occur in present day deserts. One (5) ______ is the bizarre conifer relative tumboa, in the Namib Desert of southwestern Africa.