Which three statements about subqueries are true?（） A single row subquery can retrieve only one column and one row.。 A single row subquery can retrieve only one row but many columns.。 A multiple row subquery can retrieve multiple rows and multiple columns.。 A multiple row subquery can be compared by using the “>” operator.。 A single row subquery can use the IN operator.。 A multiple row subquery can use the “=” operator.。
电脱水器和电脱盐器为什么要保持高压，因为：（） 高压易于破坏乳化液粒子。 阻碍电流，使电力消耗减少。 使乳化液粒子接近并促进粒子生长，便于分离。 防止产生气体。
The validate_password plugin is loaded and displays the following settings in global variables: Mysql＞ SHOW VARIABLES LIKE ‘validate_password%’; When attempting to set your password, you get the following error: Mysql＞ SET PASSWORD = PASSWORD (‘Hoverl@%’); ERROR 1819 (HY000): Your password does not satisfy the current policy requirements What is the cause of the error?（） The password is eight characters long, but needs to exceed validate_password_length to be valid。 All of the MEDIUM password policy requirements have not been honored。 The password matches a substring Hover as a dictionary word。 The password does not match the validate_passoword_number_count requirement。 There is no dictionary file defined, so password validation cannot work as expected。
充装系数：标准规定的气瓶单位水容积允许充装的（）气体重量 最大。 最小。 标准。
同步电动机的启动方法有异步启动法、辅助启动法及（）。 同步启动法。 直接启动法。 变频启动法。 间接启动法。
蓄水安全鉴定程序中设计、施工、监理、运行等建设各方分别编写（）。
