Question

Describe tow changes that are harmful explain why you consider them harmful how can you prevent them

Answer 1

Rusting of iron: If bicycle's chain gets rusted it may result in the breakage of it. 
Prevention: Applying grease regularly. 

Melting of glacier (physical change): It may result in the rise of ocean level resulting in the submerging of islands and coastal areas. 
Prevention: Reducing the emissions of green house gases

Answer 2

rusting of iron :it can be prevented by painting