The binary operation $\square$ is defined as $a \square b = ab+(a+b)$, where $a$ and $b$ are any two real numbers. The value of the identity element of this operation, defined as the number $x$ such that $a \square x = a$, for any $a$, is $0$ $1$ $2$ $10$

In a detailed study of annual crow births in India, it was found that there was relatively no growth during the period $2002$ to $2004$ and a sudden spike from $2004$ to $2005$. In another unrelated study, it was found that the revenue from cracker sales ... birth rate. If cracker sale declines, crow birth will decline. Increased birth rate of crows will cause an increase in the sale of crackers.

To pass a test, a candidate needs to answer at least $2$ out of $3$ questions correctly. A total of $6,30,000$ candidates appeared for the test. Question A was correctly answered by $3,30,000$ candidates. Question B was answered correctly by $2,50,000$ candidates. Question C ... as the number answering none, how many candidates failed to clear the test? $30,000$ $2,70,000$ $3,90,000$ $4,20,000$

An automobile travels from city A to city B and returns to city A by the same route. The speed of the vehicle during the onward and return journeys were constant at $60$ km/h and 90 km/h, respectively. What is the average speed in km/h for the entire journey? $72$ $73$ $74$ $75$