Two coins $A$ and $B$ are kept in an urn. When coin $A$ is flipped,the probability of getting a Head is $1/4$,while for coin $B$ it is $3/4$. One coin is randomly chosen from this bag and tossed twice,and it falls heads on both occasions. The probability that it is coin $A$ is:

Which of the following species has no $p\pi - p\pi$ bond but has a bond order equal to that of $O_2$?

$A$ railway line is taken round a circular arc of radius $1000 \ m$,and is banked by raising the outer rail $h \ m$ above the inner rail. If the lateral force on the inner rail when a train travels round the curve at $10 \ ms^{-1}$ is equal to the lateral force on the outer rail when the train's speed is $20 \ ms^{-1}$,the value of $4g \tan \theta$ is equal to: (The distance between the rails is $1.5 \ m$).

Which air pollutant is responsible for the Bhopal gas tragedy?

The inverse of the matrix $\left[\begin{array}{ccc}7 & -3 & -3 \\ -1 & 1 & 0 \\ -1 & 0 & 1\end{array}\right]$ is

The famous botanical garden '$Kew$' is located in