【正确答案】：
LETTING MATILDA'S FATHER HOLD HER WRISTS HE TRIED HIS BEST TO OPEN HER MOUTH AND FOUND SHE REALLY HAD DIPHTHERIA.
【题目解析】：考点：手腕：wrists；用力，尽力：tryhis best。句子结构：非谓语+并列结构+宾语从句，letting是现在分词作非谓语，句子真正的谓语是tried和found，且found后面是省略that的宾语从句。
LETTING MATILDA'S FATHER HOLD HER WRISTS HE TRIED HIS BEST TO OPEN HER MOUTH AND FOUND SHE REALLY HAD DIPHTHERIA.