Hadith 18 of an-Nawawi enjoins believers to

A.

Be firm and brave

B.

Be strong-minded and clean

C.

Have piety and work righteously

D.

Acquire knowledge and be polite

Correct answer is C

On the authority of Abu Dharr, Jundub ibn Junadah, and Abu Abdul Rahman Mu'adh ibn jabal (May Allah be pleased with both of them) from the Messenger of Allah (peace and blessings of Allah be upon him) who said: "Fear Allah wherever you are. And follow up a bad deed with a good deed and it will wipe it out. And behave towards the people with good behaviour".