Questions

Here ‘passed each other’ means crossed each other’s path. No preposition is required by ‘passed’.

A search engine is a set of programs which enables users to search documents and files ihe world wide web.

Common search engines are Google, Yahoo, Bing,...

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.

Christianity was founded by hesus Christ in Jerusalem, capital of Israel.

Customer Satisfaction means, dealing with the customer in a proper or positive way. Every individual mindset is  different so their cause and satisfactory leave also changed. So the main challenge of a worker of a call center is to make them understand that they are also concerned about their trouble.

Most stars are at main sequence point in their life cycles.