Which insect is used to control the spread of prickly pear cactus $(Opuntia)$?

How are the following compounds related?

An ideal gas is taken through the cycle $A \to B \to C \to A$,as shown in the figure. If the net heat supplied to the gas in the cycle is $5\,J$,the work done by the gas in the process $C \to A$ is ...... $J$.

The perpendicular distance of the straight line $12x + 5y = 7$ from the origin is given by

If $f(x) = \frac{x^2}{x+a}$, then $f^{\prime \prime}(a)$ is equal to

$A$ rod is fixed between two points at $20^{\circ}C$. The coefficient of linear expansion of the material of the rod is $1.1 \times 10^{-5} /^{\circ}C$ and Young's modulus is $1.2 \times 10^{11} \, N/m^2$. Find the stress developed in the rod if the temperature of the rod becomes $10^{\circ}C$.