Final answer:
Strong deactivating groups typically have a positive charge, which withdraws electron density and makes a compound less reactive towards electrophilic aromatic substitution. Common examples include nitro and cyano groups.
Step-by-step explanation:
Strong deactivating groups usually have a positive charge, which makes option A the correct answer. Deactivating groups tend to withdraw electron density from the ring in aromatic compounds, making the compound less reactive towards electrophilic aromatic substitution. Those that are strongly deactivating often possess a positive charge or are capable of delocalizing the positive charge through resonance.
For example, a nitro group (-NO2) is a strong deactivating group and is often associated with a partial positive charge due to its electronegativity and ability to resonate. Similarly, cyano groups (-CN) can withdraw electron density and possess a partial positive charge. Both of these groups would result in the ring being less reactive to electrophiles.