The words to analyze are: spoken, forgotten, stolen.
Let's examine each word in the context of the letters provided:
spoken: Found in Letter 1 (Joe): "I've spoken to my parents". This is the past participle of the verb 'to speak' (speak, spoke, spoken), used here with the auxiliary verb 'have' to form the present perfect tense.
forgotten: Found in Letter 2 (Amy): "she's forgotten her sandwiches". This is the past participle of the verb 'to forget' (forget, forgot, forgotten), used here with the auxiliary verb 'is' (she's = she has) to form the present perfect tense.
stolen: Found in Letter 3 (Sarah): "They've stolen my dinner money". This is the past participle of the verb 'to steal' (steal, stole, stolen), used here with the auxiliary verb 'have' to form the present perfect tense.
Conclusion: All three words (spoken, forgotten, stolen) are past participles.