▲閱讀下文，回答第 46-50 題
     On the planet, there are five rhino species, and all their lives are considered threatened.One of the largest threats is poaching because there is a market for their horns in Asia.
    The most endangered rhino species is the northern white rhino. Sudan was the last malenorthern white rhino, and he died in 2018. Since then, there are only two of these rhinos left,and they are both female. However, there is still hope for the rhino.
    Fortunately, an international group of scientists successfully collected mature eggs fromthe two female rhinos, fertilized them using sperm from two males (who are now dead), andthey created two northern white rhino embryos. These embryos could save the species fromextinction.
【題組】46. What is the main purpose of the first paragraph?
(A) To introduce five different kinds of rhinos.
(B) To report how rhino species are threatened.
(C) To divide rhinos into different colors.
(D) To identify the gender of white rhinos.