The correct answer is: A. has begun/is returning
Tim has begun a master’s degree, and he is returning to Canada. The sentence is in the present perfect progressive tense, which is used to talk about actions that started in the past and are still happening in the present. The past participle “begun” indicates that the action of beginning the master’s degree started before the present moment, and the present participle “returning” indicates that the action of returning to Canada is still happening.
The other options are incorrect because they do not use the present perfect progressive tense. Option B, “began/returned,” uses the simple past tense, which is used to talk about actions that happened at a specific time in the past. Option C, “is beginning/returned,” uses the present progressive tense, which is used to talk about actions that are happening right now. Option D, “was beginning/returns,” uses the past progressive tense, which is used to talk about actions that were happening at a specific time in the past. Option E, “begins/has returned,” uses the simple present tense and the present perfect tense, which are used to talk about actions that happen regularly or that have happened in the past and are still true in the present.