Peter F. answered 04/01/22
Published Author; Kinder-College English Tutor w/ 18 Years' Experience
Hello 0825 2,
I can see why you thought option (a) was correct since children are/can be multitalented but get very distracted by their peers, social media, families, school, extracurricular activities, etc.
However, your teacher is correct that option (d) is correct because during the summertime, as indicated in the paragraph above, children of today tend to overwork themselves in order to stay busy and get ahead academically in preparation for the upcoming school year. And that makes themselves hardworking and determined, as indicated in option (d). There are plenty of examples of that thesis statement provided throughout the paragraph, namely here: "One would have thought the children are doing too much during their vacations and not too little, given the plethora of course, classes, camps and workshop involving swimming, art, personality development, music, computers and the like that seem to cram their calendar."
I hope this helps to answer your question! :)

Peter F.
04/02/22
0825 2.
Thanks!04/02/22