Excess of which of the following in water causes blue baby syndrome disease?

Amongst the given taxonomic aids,how many are associated with the preservation of specimens?
Monograph,Flora,Key,Museums,Botanical Gardens,Catalogue,Herbarium,Manual

The density $($in $g cm ^{-3} )$ of the metal which forms a cubic close packed $(ccp)$ lattice with an axial distance $($edge length$)$ equal to $400 \ pm$ is $....$
Use: Atomic mass of metal $=105.6 \ amu$ and Avogadro's constant $=6 \times 10^{23} mol^{-1}$

Which of the following is the characteristic outer electronic configuration of alkaline earth metals?

If the function $f$ defined on $\left( \frac{\pi }{6}, \frac{\pi }{3} \right)$ by $f(x) = \begin{cases} \frac{\sqrt{2} \cos x - 1}{\cot x - 1}, & x \neq \frac{\pi}{4} \\ k, & x = \frac{\pi}{4} \end{cases}$ is continuous,then $k$ is equal to

The resolving limit of a healthy human eye is about: