Some educators try to put students of similar abilities into the same class because they believe this kind of __________ grouping is advisable.

单项选择题Military orders are __________ and cannot be disobeyed.

单项选择题What you say now is not __________ with what you said last week.

单项选择题Many years had __________ before they returned to their original urban areas.

单项选择题All the people in the stadium cheered up when they saw hundreds of colorful balloons __________ slowly into the sky.

单项选择题We shall probably never be able to __________ the exact nature of these sub-atomic particles.