Which role is played by Lactobacillus in our stomach?

Assertion $(A)$: White tin is an example of a tetragonal system.
Reasoning $(R)$: For a tetragonal system,$a=b=c$ and $\alpha=\beta=\gamma \neq 90^{\circ}$. The correct answer is

If the coefficients of the $(2r+1)$-th term and the $(r+2)$-th term in the expansion of $(1+x)^{43}$ are equal,then $r$ is equal to:

What is $Z$ in the following reaction? $CH_3-CH_2-CO_2^{\ominus} Na^{\oplus} \stackrel{NaOH / CaO}{\longrightarrow} Z$

What is the entropy change in $J K^{-1}$ during the melting of $27.3 \ g$ of ice at $0^{\circ} C$? (Latent heat of fusion of ice $= 330 \ J g^{-1}$)

If Henle's loop were absent from mammalian nephron,which of the following is to be expected?