The correct option is A White crystalline solid
Borax is a white crystalline solid.
It is less soluble in cold water but more soluble in hot water.
Hence correct option is a.
THEORY
Properties:
Borax is a white crystalline solid.
1. It is less soluble in cold water but more soluble in hot water.
2. Its aqueous solution is alkaline.
Na2B4O7+7H2O→4H3BO3+2NaOH
3. Effect of heating: It first swells due to loss of water in the form of steam
Na2B4O7.10H2O△→Na2B4O7+10H2O
Na2B4O7△→2NaBO2+B2O3 Sodium metaborate