下列叙述正确的是( )
A:蝌蚪不仅用鳃呼吸,还用肺呼吸,因此称为两栖动物
B:青蛙在生殖季节,雌雄抱对,进行体内受精
C:青蛙的发育经历了受精卵、蝌蚪、成蛙三个时期
D:两栖动物是由水生向陆生过渡的类群
— I hear that John has gone to Japan for a visit. Do you know it? — He made no ________ of his journey before.
若手指划破后感染发炎,血检时往往会发现血液中哪一种成分增多( )