If $(2, 0)$ is the vertex and the $y$-axis is the directrix of a parabola,then its focus is

If $A+C=2B$,then $\frac{\cos C-\cos A}{\sin A-\sin C}$ is equal to

Calculate the heat of combustion (in $kJ$) of methane from the following data:
$(I)$ $C_{(graphite)} + 2H_{2(g)} \rightarrow CH_{4(g)} \quad \Delta H = -74.8 \ kJ$
$(II)$ $C_{(graphite)} + O_{2(g)} \rightarrow CO_{2(g)} \quad \Delta H = -393.5 \ kJ$
$(III)$ $H_{2(g)} + 1/2 O_{2(g)} \rightarrow H_2O_{(l)} \quad \Delta H = -286.2 \ kJ$

The radius of Germanium $(Ge)$ nuclide is measured to be twice the radius of $_{4}^{9}\text{Be}$ . The number of nucleons in $Ge$ are

Which structure acts as the pacemaker of the heart?

Which of the following is a characteristic of $Pteridophytes$?