1 . The first challenge for all the learners ______(involve) in the e-learning area is that your contents should be available on smartphones and mobile Internet devices. (用所给词的适当形式填空)

2 . I always dream of having a house ________ by trees, flowers and grass. If I can live in such beautiful ________, I must feel happy every day. As we know, the ________ things can always have an effect on our mood. (surround)(所给词的适当形式填空)

3 . These boats catch large numbers of fish without giving them time to lay eggs, which will result in a smaller number of fish ________ (leave) to eat. (所给词的适当形式填空)