_______ is a response to pressure exerted by norms that are generally left unstated

It is difficult to distinguish between colors at night because ______

a) we are seeing primarily with the cones b) rods do not adapt to the dark c) we are seeing primarily with the rods d) we are used to seeing mostly with the fovea

Rex describes a period of the lifespan as "the time when primitive organ systems mature and become functional." The period he is describing would correctly be identified as:

a. the germinal period b. the fetal period c. the embryonic period d. the viability period