Which of the following gases has the highest heat of combustion?

In the circuit,if the forward voltage drop for the diode is $0.5 \, V$,the current will be........$mA$.

In a $U$-tube experiment,a column $AB$ of water is balanced by a column $CD$ of oil,as shown in the figure. Then the relative density of oil is

An ideal coil of $10\, H$ is connected in series with a resistance of $5\, \Omega$ and a battery of $5\, V$. After $2\, s$,after the connection is made,the current flowing (in ampere) in the circuit is.

Name the method of asexual reproduction in lichens.

If the pair of straight lines $6x^2 - 5xy + y^2 = 0$ makes angles $\alpha$ and $\beta$ with the $X$-axis,then $\tan(\alpha - \beta) = $