In the reaction of $BaO_2$ with dilute $H_2SO_4$,what are the oxidation states of the most electronegative element in the products?

In a $\triangle ABC$,if $\frac{a}{b^2-c^2} + \frac{c}{b^2-a^2} = 0$,then $B$ is equal to

$A$ steady current flows in a long wire. It is bent into a circular loop of one turn and the magnetic field at the centre of the coil is $B$. If the same wire is bent into a circular loop of $n$ turns,the magnetic field at the centre of the coil is

It is now possible to breed plants and animals with desired characters through:

Given that:
$2C_{(s)} + 2O_{2(g)} \to 2CO_{2(g)}; \Delta H = -787 \ kJ$
$H_{2(g)} + 1/2 O_{2(g)} \to H_2O_{(l)}; \Delta H = -286 \ kJ$
$C_2H_{2(g)} + 2.5 O_{2(g)} \to 2CO_{2(g)} + H_2O_{(l)}; \Delta H = -1301 \ kJ$
Calculate the heat of formation of acetylene $(C_2H_{2(g)})$ in $kJ$.

$p$ points are chosen on each of the three coplanar lines. The maximum number of triangles formed with vertices at these points is