In bryophytes and pteridophytes,transport of male gametes requires:

For the alkali metals,which of the following increases with increasing atomic number?

If $x^2+2px-2p+8>0$ for all real values of $x$,then the set of all possible values of $p$ is

What is obtained by the decomposition of sodium nitrate at a temperature above $800\,^oC$?

Consider the statements given below regarding contraception and answer as directed thereafter:
$(1)$ Medical Termination of Pregnancy $(MTP)$ during the first trimester is generally safe.
$(2)$ Generally,chances of conception are nil until the mother breast-feeds the infant up to two years.
$(3)$ Intrauterine devices like Copper-$T$ are effective contraceptives.
$(4)$ Contraception pills may be taken up to one week after coitus to prevent conception.
Which two of the above statements are correct?

If the normal to the curve $y = f(x)$ at the point $(3, 4)$ makes an angle $\frac{3\pi}{4}$ with the positive $x$-axis,then $f'(3)$ is equal to