Which of the following is a heterosporous pteridophyte?

$A$ force of $(3\hat i + 4\hat j)\, N$ acts on a body and displaces it by $(3\hat i + 4\hat j)\, m$. The work done by the force is ............. $J$.

$A$ steel meter scale is to be ruled so that millimeter intervals are accurate within about $5 \times 10^{-5} \ m$ at a certain temperature. The maximum temperature variation allowable during the ruling is (Coefficient of linear expansion of steel $= 10 \times 10^{-6} \ K^{-1}$) (in $^{\circ} C$)

The sum of the fourth powers of the roots of the equation $x^3+x+1=0$ is

Which of the following salts does not give a flame test?

If the lines,joining the origin to the points of intersection of the curve $2x^2 - 2xy + 3y^2 + 2x - y - 1 = 0$ and the line $x + 2y = k$,are at right angles,then $k^2$ equals