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

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 $\text{ h}$)?

Which of the following is not a polyamide?

Differentiate the function with respect to $x$: $\sec (\tan (\sqrt{x}))$

Which of the following is the family of sunflower?

Which artery is absent in a frog?