Step 1: Understanding verb forms.
The word “got” is a helping verb here. When “get” is used in the passive form (to show that something happened to the subject), it is followed by the past participle (V3) form of the verb.
Step 2: Analyze the options.
- (a) stolen: Past participle (V3) form — correct.
- (b) steal: Base form (V1) — incorrect.
- (c) stole: Simple past (V2) — incorrect.
- (d) stealed: Not a correct English form.
Step 3: Grammar rule.
Structure: “get + past participle” is used to indicate that something happened to the subject.
Example: “My phone got broken.” / “Her bag got lost.”
Step 4: Constructing the correct sentence.
“I don’t know how the money I kept in my wallet got stolen.”
Step 5: Conclusion.
The correct verb form is “stolen.”