A.無(wú)神經(jīng)—梯神經(jīng)—索式神經(jīng)—鏈狀神經(jīng) B.無(wú)神經(jīng)—網(wǎng)神經(jīng)—梯神經(jīng)—索式神經(jīng)—鏈狀神經(jīng) C.無(wú)神經(jīng)—索式神經(jīng)—網(wǎng)神經(jīng)—鏈狀神經(jīng) D.無(wú)神經(jīng)—梯神經(jīng)—鏈狀神經(jīng)
A.扁形動(dòng)物 B.原腔動(dòng)物 C.腔腸動(dòng)物 D.環(huán)節(jié)動(dòng)物.