Clot
clots
land
lands
lots
slot
loan
loans
slant
sand
coal
coals
The correct answer is - Watershed.
The drainage basis are places in which all the water in an area is accumulated and ends up in the same place. The drainage systems are divided by highlands, which can vary from small hills to very high mountains, depending on the topography of the place.
The line on the highland that is separating the drainage systems is called watershed. The watershed is simply a line stretching on the highest parts of a highland, thus having a slope on each side.
You didn't give your choices but sin 21 equals 0.358.
