Subject-verb agreement with ‘both…and’, ‘one of … who…’ and ‘the only one of… who…’

• You put the verb in the plural with both … and: 

Both my lecturer and my tutor agree. 

• With one of… who…, use the verb in the plural: 

Thomson is one of the researchers who agree with that view. 

• With the only one of… who…, use the verb in the singular: 

Thomson is the only one of the researchers who agrees with that view.