C 3 plants are more efficient at conversion of sunlight to plant ...

[newyorker26]

C 3 plants are more efficient at conversion of sunlight to plant matter than C4 plants.
 
  What will be an ideal response?

Question 2

Ref. 59 finds that lead deposition decreases after 1979 . What could be the reason? Suggest a possible answer. Justify your suggestion.
 
  What will be an ideal response?

[TDubDCFL]

Answer to Question 1

The reverse is true. At high light levels, C4 plants are more efficient. Also, they are
more efficient users of water (corn Zea mays, for example, is a C4 plant). Efforts are
under way to increase plant efficiency from multiple approaches for both types of plant, but
especially for C3 food crops.

Answer to Question 2

The reduction and then, finally, elimination of tetraethyl lead from gasoline (it
increased octane number cheaply) is the likely cause of the observed reduction in the
amount of lead deposition.

[newyorker26]

TYSM

[milbourne11]

Excellent