Which of the following is a prokaryotic kingdom?

Two workers $A$ and $B$ are engaged to do a piece of work. Working alone,$A$ takes $8 \text{ h}$ more to complete the work than if both worked together. On the other hand,working alone,$B$ would need $4 \frac{1}{2} \text{ h}$ more to complete the work than if both worked together. How much time would they take to complete the job working together (in $\text{ h}$)?

The energy required to accelerate a car from $10 \, m/s$ to $20 \, m/s$ is how many times the energy required to accelerate the car from rest to $10 \, m/s$?

Which of the following ecosystem types has the highest annual net primary productivity?

The angle of a prism is $A.$ One of its refracting surfaces is silvered. Light rays falling at an angle of incidence $2A$ on the first surface return back through the same path after suffering reflection at the silvered surface. The refractive index $\mu$ of the prism is

If $\frac{1+\sqrt{3}i}{2}$ is a root of the equation $x^4-x^2+x-1=0$,then its real roots are: