Which amongst the following is the strongest acid?

Identify the most stable species in the following set of ions giving reasons.
$(a) \ \stackrel{+}{C} H_{3}, \stackrel{+}{C} H_{2} Br, \stackrel{+}{C} HBr_{2}, \stackrel{+}{C} Br_{3}$
$(b) \ \stackrel{\Theta}{C} H_{3}, \stackrel{\Theta}{C} H_{2} Cl, \stackrel{\Theta}{C} HCl_{2}, \stackrel{\Theta}{C} Cl_{3}$

Given below are two statements:
Statement $I$: In $O_2N-C_6H_4-CH^+-C_6H_4-OCH_3$, the carbocation is stabilised by $+R$ effect of $-OCH_3$ group.
Statement $II$: In $O_2N-C_6H_4-CH^--C_6H_4-OCH_3$, the carbanion is stabilised by $-R$ effect of $-NO_2$ group.
In the light of the above statements, choose the correct answer from the options given below:

Rank the following compounds in the order of increasing acidic strength:

Which of the following is correct?

Which of the following statements are not correct?
$a$. The energy of resonance hybrid structure is higher than that of the possible canonical structures of the molecule.
$b$. When inductive effect and electromeric effect operate in opposite directions,electromeric effect predominates.
$c$. When the $\pi$ electrons of the multiple bond are transferred to that atom to which the attacking reagent does not get attached,it is known as $+E$ effect.
$d$. The resonance structures with separation of opposite charges are more stable.