Right underneath the word "Valley" on the topographic map is the main river flowing through this valley. Follow along this river in both directions on the map. Now notice at several points along the river there are tributary streams feeding into it at near right angles. Also notice that the contour lines point upstream as they intercept the tributary streams. This is a V shaped river valley with a main river flowing through it and tributaries flowing down the sides of it. Consequently, this is a trellis drainage system (B). For a further explanation of drainage systems, see questions #3 and #6.