Final answer:
Iago manipulates Roderigo into believing Desdemona loves Cassio through suggestive language and playing on Roderigo's emotions, despite the lack of evidence.
Step-by-step explanation:
Iago attempts to convince Roderigo that Desdemona is in love with Cassio by using insinuations and half-truths. He suggests that Desdemona's affections are fickle and that she is naturally inclined to desire new experiences and people. Iago plays on Roderigo's jealousy and desperation to shape his perception, despite the lack of concrete evidence. He does this by questioning Desdemona's sincerity and loyalty and by implying that her alleged passion for Cassio is a result of her unfaithfulness to Othello and an attraction to Cassio's manners and good looks.