Exercise 2 solution

Example answer (yours will differ):
Possible reasons: soil too cold in March; seed too old; sown too deep; seedbed dried out or capped hard after rain; seed washed away or eaten by slugs or birds; not enough time yet (carrots can take 2-3 weeks or more).
Check first: dig gently along the row for rotted or sprouted seed; check the seed date; feel whether the soil surface is dry or crusted.
Fix: resow in April or May into a fine, moist seedbed about 1 cm deep, and keep it damp until seedlings appear. A board or fleece over the row helps hold moisture.