Questions

The United States subprime mortgage crisis was a nationwide financial crisis, occurring between 2007 and 2010, that contributed to the U.S. recession of December 2007 –June 2009.It was triggered by a large decline in home prices after the collapse of a housing bubble, leading to mortgage delinquencies and foreclosures and the devaluation of housing-related securities.

It is due to the deficiency of Vitamin A. Retinol which is present in vitamin A. Its deficiency causes night blindness. It is available in carrots. 

Among the given options, Tata Steel company received the award as one of the 2019 World’s Most Ethical Companies.

The given sentence is in simple present tense and states a general fact, hence the latter half of the sentence with the blank will also be in the simple present tense. Since the subject in the latter part of the sentence is singular .i.e. 'the number', the verb will be followed accordingly. Hence, option 4 is the correct answer.

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