Questions

Soviet Union

When water is cooled from 4°C to 0°C, its density decreases.

When water cools from 4°C to 0°C, ice crystals begin to form because the water is approaching its freezing point. When water freezes, the water molecules form a lattice that increases the volume. As a result, the density decreases. This is why ice will float on top of water; ice has a lower density than the water.

Tetrad is a homologous chromosome pair in the given options. A homologous chromosome pair is a pair of chromosomes one from father and one from mother that has same gene sequence after the process of meiosis.

A man with colour blindness will see red and green as same. 

When hierarchical routing is used, the routers are divided into what we call regions, with each router knowing all the details about how to route packets to destinations within its own region, but knowing nothing about the internal structure of other regions

‘has’ is incorrectly used since the sentence is in past tense. Moreover, the subject is cities, which is plural.