Why are hydrogen bonds the strongest of the intermolecular forces?

a. hydrogen forms covalent bonds
b. hydrogen forms polar bonds
c. hydrogen lacks the protection of inner electron shells
d. hydrogen is protected by four outer electron shells

The correct answer is c. 
answer b is incorrect 

Olá. porque a reação na temperatura é muito rapida a do copo : )

The population of unionid mussels decreased after zebra mussels were introduced. zebra mussels competed with the unionid mussels for food. the zebra mussels were able to displace the unionid mussels, allowing the zebra mussel population to increase  over the years. the unionid mussel population decreased because  of lack of food.