The reproductive tract of stallion has two of each of the following structures EXCEPTfor one of them. Which structure is present as a single structure?

A．They found ways to speed up the reproduction of bald eagles.B．They developed new typ

A．They found ways to speed up the reproduction of bald eagles.B．They developed new typ

A．They will face extinction without artificial reproduction.B．They will have to migrat

A．The change of lifestyle.B．The change of the nature of occupations.C．The increase of

听力原文：Because of the decreasing sales of the products at the end of the year, the sales

What is the passage mainly about？A．Reproduction in echinoderms.B．How fish avoid their enem