See ↑ BELIEVE 3, ↑ DOUBT 1, ↑ SURE/NOT SURE 3
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• ↑ be in doubt
• ↑ beyond a shadow of a doubt
• ↑ give sb the benefit of the doubt
• ↑ have no doubt
• ↑ there's no doubt/there's no question
• ↑ undoubtedly/unquestionably/without doubt/without a doubt