Exercise 1 solution

Exit pupil = objective diameter / magnification.
(a) 8x32: 32 / 8 = 4 mm
(b) 10x32: 32 / 10 = 3.2 mm
(c) 8x56: 56 / 8 = 7 mm
(d) 12x50: 50 / 12 = 4.17 mm (about 4.2)

Daylight eye pupil is about 3 mm (per the chapter's source), so the 10x32 comes closest and wastes the least light in bright conditions. The 8x56 matches the roughly 7 mm night pupil, so it suits dusk, but it is large and heavy.