Which of the following is a true acidic anhydride?

If $\cos x + \cos^2 x = 1$,then the value of $\sin^2 x + \sin^4 x$ is

Which of the following substances has the highest melting point?

Which one of the following correctly represents the variation of electronegativity $(EN)$ with atomic number $(Z)$ of group $13$ elements?

If $f: R \rightarrow R$ is defined by $f(x) = [\frac{x}{5}]$ for $x \in R$,where $[y]$ denotes the greatest integer not exceeding $y$,then $\{f(x) : |x| < 71\}$ is equal to

Which of the following has the smallest size?