________hehasmanyfriends,heisoftenfeelinglonely.
Sofarscientistshaveonlyacquired________understandingofthephysicalprocessesthatcauseearthquakes.
Wehave______at30days’sightfortheamountoftheinvoice.
IntheGrammar-TranslationMethod,understandingandmemorizationof_____________wereregardedasimportantmeansofdevelopingmentality.
名词解释：copyright
