It's kind_________ you to help organize our Helping Hands Meeting because it's still difficult _________ the children in poor areas to go to school.
给出下列长度的四组线段：①1，2，2；②5，12，13；③6，7，8；④3m，4m，5m（m＞0）.其中能组成直角三角形的有（ ）
