To conserve energy the genes in e. coli are
always active
never active
only active when needed
nonfunctional
!

in cartography, a contour line (often just called a "contour") joins points of equal elevation (height) above a given level, such as mean sea level. a contour map is a map illustrated with contour lines, for example a topographic map, which thus shows valleys and hills, and the steepness or gentleness of slopes.

explanation:

the answer is b & c i believe : )