在软土地区基坑开挖深度超过( )m,一般就要用井点降水。
患者,女,29岁。已婚2年一直未孕,既往月经周期正常,行经期4~6天。现停经45天,突然左下腹撕裂样剧痛,并伴头晕恶心,面色苍白。下列措施错误的是
If two phonetically similar sounds are two distinctive phonemes,they are said to form a_______.