Which of the following statement is incorrect about nucleophiles?

• A. Nucleophiles have an unshared electron pair and can make use of this to react with an electron deficient species
• B. The nucleophilicity of an element (an electron donor) generally increases on going down a group in the periodic table
• C. A nucleophile is electron-deficient species
• D. All good nucleophiles are good bases when we deal across the period