A common existing technique for assessing the provitamin A content of corn varieties can be prohibitively expensive for plant breeders, the researchers said, but the new one is vastly less expensive.是什么意思_A common existing technique for assessing the provitamin A content of corn varieties can be prohibitively expensive for plant breeders, the researchers said, but the new one is vastly less expensive.在线翻译_英语_读音_用法_例句