Question

mountaineers may suffer from nose bleeding at high altitudes

Answer 1

atmospheric pressure at high altitude is less than that on ground
so when mountainers reach high altitudes the small blood capillaries in nasal canal ruptures and leads to bleeding

Answer 2

As the altitudes increases the pressure decreases and the air becames thinner and there will be very less oxygen at high altitudes. So due to which blood vessels present inside our nose brust and starts bleeding