Petroleum is a mixture of
1). elements
2). hydrocarbons
3). polymers
4). salts
1. Symbiotic Bacteria responsible for the fixation of atmospheric nitrogen are present in
2. The major harmful gas emitted by automobile vehicles which causes air pollution is
3. What material is used to make electric heater coil
4. Which of the following is used for refrigeration?
5. What is the process of conversion of solid state directly to gaseous state called ?
6. Among the following the hardest metal is