Which one of the following gas was not present in free form at the time life originated on earth?

The most thoroughly studied of the known bacteria plant interactions is the

Match the following by using codes:

$A.$ Vernalization                         -          $1. $ Camerarius

$B.$ Double fertilization                -          $2.$  Hofmeister

$C.$ Pollination                             -          $3. $ Lysenko

$D.$ Alternation of Generations    -          $4. $ Nawaschin

The scientist related with the over throw or the "Theory of spontaneous generation'' and experiments with swan-necked flasks is

Assertion : From evolutionary point of view, human gestation period is believed to be shortening.

Reason : One major evolutionary trend in humans has been the larger head undergoing relatively faster growth rate in the foetal stage.

Coacervates are