Questions

Guglielmo Marconi, an Italian invetor invented Radio in 1890's.

When heated any substance, the molecules move apart from each other. Alike in the air the molecules move apart from each other. We know that the warm air is lighter than the cool air. Since after heating air gets warmer, it floats up and the cool air comes down to occupy the warm air place.

The South American countries that lie within the Tropic of Capricorn are Argentina, Brazil, Chile and Paraguay. Brazil is the only country in the world that crosses both the Equator and either tropic.

Br-Br.

In Br2, two of the same atoms, pull on each side of the bond is equal making it as non-polar.

The other options all include a significantly more electronegative atom (the oxygens and the chlorine), so those bonds are all polar covalent.

In DNA, adenine pairs with Thymine. Similarly, in RNA, due to absence of thymine in RNA and the same structure with uracil helps to pair with adenine.