The frequency of the tuning fork is $n$ and $l_1$ and $l_2$ are the length of the first and second resonating column. Which one of the following is the formula used for the calculation of the speed of air using the resonance tube?

In the following passage there are blanks, each of which has been numbered. There are questions given below the passage and for each question, four words are suggested, one of which fits the blank appropriately. Find out the appropriate word in each case.

Whenever I go into a bank, I feel scared. Everybody and everything that I see there (1) ____ me. As for the manager the sight (2) ____ him simply terrifies me and (3) ____ me want to runaway (4) _____ I can. As soon as I (5) ____ the door of the bank I lose my head (6) ____ when I try to do any (7) ____ there, I behave like an idiot. I cannot explain (8) ____ for this but that is how it (9) ____ has been that is how it is (10) ____.

Select the most appropriate option for blank No. 10.

For given diagram choose the correct option for $X$, $Y$, and $Z$: