Accordingtothe"principles-and-parameters"theory,"principles"refertohighlyabstractpropertiesofgrammarwhichareappliedtolanguageingeneralandwhichgeneratephrasesandatthesametimerestrainthepowerofMovea,while"parameters"allowgeneralprinciplestooperateincertainrestrictedways,accordingtowhichparticulargrammarsofnaturallanguagesvary.

This is an important problem _______ too few social scientists have researched.

By"languageacquisitionisprimarilytheacquistionofthegrammaticalsystemoflanguage",linguistsmeanthat______.

The reply, when it finally came, was ________ the negative.

If you are walking away from a clock tower ，you will hear the ticking of the clock fade to a point ________ it cannot be heard.