1. smartphones are used not only for communication but also for information and entertainment (entertain)
- The word "entertain" is used to describe the additional purpose of smartphones, which is to provide entertainment to users. This can include activities such as playing games, watching videos, or listening to music.

2. it is surprising that all the students in class 10B choose to do a project on helping the needy (surprise)
- The word "surprise" is used to express astonishment or unexpectedness. In this context, it is unexpected or surprising that all the students in class 10B have chosen to work on a project focused on helping those in need.

3. these children encounter many problems and really need our help (advantage)
- The word "advantage" is not suitable in this context. It would be more appropriate to use a word like "disadvantage" or "challenge" to describe the difficulties faced by these children.

4. fundraising for charity is a meaningful thing for everyone to do to help the community (fund)
- The word "fund" is used to describe the act of raising money for a specific cause or organization. In this sentence, it is stating that fundraising for charity is a meaningful activity that everyone can participate in to support and benefit the community.