In the Romer Model, the Growth Rate of Ideas

In the Romer model, the growth rate of ideas, , is increasing in the:

A) share of the population doing research and the total population.
B) knowledge efficiency parameter and the population growth rate.
C) knowledge efficiency parameter, the research share, and the total population.
D) knowledge efficiency parameter and the saving rate.
E) share of population engaged in research and development and the saving rate.