Late frost would damage the orchard. Which sentence contains an error involving unless in the first-conditional forms topic?
Unless late frost arrives, the orchard should produce a full crop.
If the parcel locker is full, leave the package at reception.
Unless late frost does not arrive, the orchard should produce a full crop.✓Respuesta correcta
If the licence is approved, the café may add pavement tables.
Explicación
The harvest sentence contains the error because unless already means if not, so do not arrive reverses the intended condition. An affirmative present form is needed to mean that frost failing to arrive preserves the crop.