In which of the following is the notochord present in the embryonic stage?

The number of subsets of $\{1, 2, 3, \ldots, 9\}$ containing at least one odd number is

The shortest distance between the line $y-x=1$ and the curve $x=y^2$ is

The condition that $f(x)=a x^3+b x^2+c x+d$ has no extreme value, is

$A$ molecule $M$ associates in a given solvent according to the equation $nM \rightleftharpoons (M)_n$. For a certain concentration of $M$,the van't Hoff factor was found to be $0.9$ and the fraction of associated molecules was $0.2$. The value of $n$ is:

Which pair of oxyacids of phosphorus contains $P-H$ bonds?