Which of the following is an electrophilic reagent?

What is the decreasing order of basic strength for the following species: $\mathop O\limits^\Theta H, \mathop N\limits^\Theta H_2, HC \equiv \mathop C\limits^\Theta, CH_3 - \mathop C\limits^\Theta H_2$?

The cyanide ion $(CN^-)$ acts as an ambident nucleophile. From which end does it act as a stronger nucleophile in an aqueous medium? Give a reason for your answer.

Which one of the following series contains electrophiles only?

What is the decreasing order of nucleophilicity for $R_3C^{-}, R_2N^{-}, RO^{-},$ and $F^{-}$?

Giving justification,categorise the following molecules/ions as nucleophile or electrophile: $HS^{-}, BF_{3}, C_{2}H_{5}O^{-}, (CH_{3})_{3}N:, \overset{+}{Cl}, CH_{3}-\overset{+}{C}=O, H_{2}N:^{-}, \overset{+}{N}O_{2}$