I am very interesting in problems caused by pollution.

        A                   B                                C               D

Even on the most careful prepared trip, problems will sometimes develop.

         A                            B                     C                                       D

The package must be wrapped carefully before it is post.

                 A                     B                                C           D

It was such a difficult homework that it took me two hours to finish it.

            A          B                                  C                                           D

The teacher asked him why hadn't he done his homework, but he said nothing.

                                              A              B                                     C              D

Of all the portraits he has painted, I like this one more.

    A                                         B             C                   D

I often look into new words in the dictionary whenever I don't know their meanings.

                   A                        B                                C                              D

Although his family is poor, but he studies very well.

                                       A            B           C               D