Complementary goods are goods that are used together. The consumption of one good typically enhances the consumption of the other. In this case, a toothbrush is complementary to toothpaste because both are typically used together for oral hygiene.
- (A) Oats and Jam Rolls: Not complementary; oats and jam rolls are not typically consumed together in a complementary fashion.
- (C) Petrol cans and Electric cars: Not complementary; petrol is used for combustion engine vehicles, whereas electric cars use electricity.
- (D) LPG and CNG: Both are types of fuel, but they are not complementary in the way that toothpaste and toothbrush are.
Final Answer: (B) Toothbrush and Toothpaste.