About Dumbledore 's absolute trust in Severus . And then Tonks lied . She pretended that she herself did n't know the reason why Dumbledore trusted Severus . ' But Dumbledore swore he was on our side ! ' said Tonks urgently , trying to convince herself more than anything .

Based on the preceding passage, choose your answer for question Why did Tonk lie to herself about Severus ?
Options:
[a]. Tonks lied to herself because she wanted to be convinced .;
[b]. Tonk lied to herself because she wanted to believed in Dumbledore .;
[c]. Tonks lied to herself because she wanted Severus to be trustworthy .;
[d]. Tonks lied to herself because Dumbledore would have wanted her to .;
The answer is:
[b].