A.1840 B.1903 C.1906 D.1919
A.市場(chǎng)主體準(zhǔn)入行為 B.市場(chǎng)主體退出行為 C.市場(chǎng)交易行為 D.市場(chǎng)競(jìng)爭(zhēng)行為