About Dike roads and mountain driving: which statements are correct? (multiple answers possible)
When climbing a mountain it is best to shift to a higher gear, so the engine does not have to work as hard.
Take descents in the same gear as the climbs and make use of the engine's braking effect; do not drive with dragging brakes.
In neutral you lose the engine's braking effect entirely, while the book precisely advises using that braking effect.
On a mountain road descending traffic has priority over climbing traffic, because braking while descending is harder.
Explanation
Book p.69-70 - do not drive up the mountain in too high a gear; the engine is better off revving more than being lugged, because too few revs raise the engine temperature considerably and increase the risk of engine damage — trap: flat-road rule of thumb (higher gear is gentler) applied to a climb.