I gave some money to Radha. 

Change the above sentence into passive voice.

When the verb's subject (in the sentence) receives the action named in the verb, the verb is said to be in the passive voice. According to the rule on changing active voice into passive, if a sentence is in past indefinite/simple past tense, to convert into passive voice, then given sentence's helping verb change into (was/were + past participle form of the verb). Therefore, option B is correct.