四、用方框中所给词语的适当形式填空，每词仅用一次
in return me hobby solve even if
I'm a maths problem collector. I enjoy the time spent with these challenging questions, 1 it always takes me over one hour to solve one of them.
Besides collecting and solving those questions, I also like to create some fun questions by 2 , especially when I don't have any maths problems 3 . Sometimes I give the newly created ones to my friends. And they give me theirs 4 ! Creating questions is much more difficult than working out the ready-made ones. Because of these strange 5 , I do well in maths tests. Moreover, I have discovered the beauty of maths, and will stick to it for a long time!

1. even if
2. myself
3. to solve
4. in return
5. hobbies

【解析】
1. 空处前后存在让步逻辑：“我享受和这些有挑战性的题目相处的时光”和“解一道题总要花我一个多小时”，even if意为“即使”，符合语境。
2. 此处是固定搭配by oneself，表示“独自、靠自己”，将me变为反身代词myself，符合“我自己出趣味题”的语义。
3. 此处是固定结构have sth. to do，表示“有某事要做”，用solve的不定式形式to solve，作后置定语修饰maths problems。
4. 前文提到我把新出的题目给朋友，此处表示朋友把他们的题目给我作为回报，in return意为“作为回报”，符合语境。
5. 空前的these表示复数概念，将hobby变为复数形式hobbies，指代前文提到的收集题、解题、出题这类爱好。
【答案】
1. even if
2. myself
3. to solve
4. in return
5. hobbies
【知识点】
词语适当形式填空；固定搭配；名词复数
【点评】
本题考查对语境逻辑的理解和基础英语固定搭配、词形变换的掌握，需要结合句子语义和语法规则，从给定词中筛选并变换出正确形式，每词仅用一次的要求也需要学生做好全局统筹。
【难度系数】
0.7