They improved their studies and had better moods./They improved maths, science and language skills and felt happier and more energetic.
题意:根据这项研究,加拿大儿童在学习一门乐器后有什么变化?
根据第二段:
The researchers tracked the school children for nine months in Canada and found that learning to play an instrument could help school children improve maths, science and language skills. Besides, children who learned to play an instrument were happier and more energetic.(研究人员对加拿大的学龄儿童进行了为期9个月的跟踪调查,发现学习一门乐器可以帮助学龄儿童提高数学、科学和语言技能。此外,学会演奏乐器的孩子更快乐,更有活力。)
可知学习一门乐器可以帮助他们提高学习成绩,心情更好。/他们提高了数学、科学和语言技能,感到更快乐、更有活力。
故答案为:They improved their studies and had better moods./They improved maths, science and language skills and felt happier and more energetic.