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a wealth of subjects is is the most popular phrase on the web. 

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• a range of problems is or a range of problems are?
• a number of students are or a number of students is?
• a number of is or a number of are?
• a wealth of subjects is or a wealth of subjects are?
• a lot of advantages is or a lot of advantages are?
• a number of people are or a number of people is?