例句 1：The report is detailed, and the solution lies therein.
例句 2：She found therein the inspiration she had been seeking for years.
例句 3：The contract is complex, but all obligations are specified therein.
例句 4：Within the ancient manuscript, therein lies a secret code.
例句 5：He discovered a world of knowledge therein that changed his life.
用法说明："Therein" 是一个正式用语，意为“在其中”或“在那里”，常用于书面语或法律、学术文本中，指代前文提到的某个事物内部。