Which cleansing agent gets precipitated in hard water?

How are transparent soaps manufactured?

Which of the following statements are not correct?
$a$) Antihistamine also functions as an antacid
$b$) The shape of an active site of an enzyme does not change when the drug binds to an allosteric site
$c$) Chemical messengers communicate the message between two neurons
$d$) Potassium soaps are hard,while sodium soaps are soft to skin
The correct answer is

$A$ neutral fertilizer among the following compounds is

Identify the use of the given drug.

Match the column:

Column-$I$ (Structure)	Column-$II$ (Cleansing agents)
$(i) CH_3(CH_2)_{16}COO(CH_2CH_2O)_nCH_2CH_2OH$	$(a)$ Cationic detergent
$(ii) C_{17}H_{35}COO^-Na^+$	$(b)$ Anionic detergent
$(iii) CH_3(CH_2)_{10}CH_2OSO_3^-Na^+$	$(c)$ Nonionic detergent
$(iv) [CH_3(CH_2)_{15}N(CH_3)_3]^+Br^-$	$(d)$ Soap