Typhoid fever is caused by which of the following?

The equation of a stationary wave along a stretched string is given by $y = 5 \sin \frac{2\pi}{3}x \cos 40\pi t$,where $x$ and $y$ are in $cm$ and $t$ is in $s$. The separation between two adjacent nodes is ..... $cm$.

$A$ neutrino is a particle,which is

From the top of a hill $h$ metres high,the angles of depression of the top and the bottom of a pillar are $\alpha$ and $\beta$ respectively. The height (in metres) of the pillar is

Acetaldehyde cannot give:

If $1, \log_9(3^{1-x} + 2), \log_3(4 \cdot 3^x - 1)$ are in $A.P.$,then $x$ equals