We found                     very difficult to learn Japanese.

       A．this                 B．that                 C．it                     D．its

________is difficult to work on the Great Green wall.

[　　]

________is easy to learn English.

[　　]

We find _____ important to use a foreign language well.

A．that              B．it                C．this              D．its

He found ________ important to study English well...

[　　]