The answer is; opioids
These painkillers relieve pain by competing with neurotransmitters in binding neurotransmitter receptors in the synapse. However, they don’t induce an impulse hence block the receptors from neurotransmitters. This working principle, however, is also problematic because it causes slow breathing because the drugs calm nerve activity even that which controls your breathing.
The right option is a. contour interval
The difference in elevation between the highest and lowest contour lines on a topographical map is called contour interval.
A contour interval is the vertical distance between the two contour lines (highest and lowest) in a topographical map. The contour interval is usually stated explicitly on the right-hand lower part in every map. 20 feet for a 1:24,000 map scale is the frequently used contour interval and different contour intervals is available for different maps.