“可燃冰”被视为21世纪的新型绿色能源．科学家估计，全球海洋底部可燃冰分布的范围约4000万平方公里，储量可供人类使用约1000年．我国南海海底存储着丰富的可燃冰资源，已经查明的储量相当于目前陆上石油、天然气资源量总数的三分之一．可燃冰的主要成份是甲烷，1m³可燃冰可转化生成164m³的甲烷气体和0.8m³的水，已知甲烷气体的热值为3.6×10⁷ J/m³．桂林市新开通的301路公交车，使用LNG天然液化气为燃料，这种燃料的主要成份就是甲烷．如果301路公交车满载乘客时总质量是6000kg，1m³可燃冰转化生成的甲烷气体完全燃烧产生的能量，可供公交车满载时以36km/h的速度匀速行驶1640min，行驶中公交车受到的平均阻力为车重的0.05倍，则这段时间内发动机的实际功率和效率各为多大？（g=10N/kg）

在含盐30%的盐水中，加入5克盐和10克水，此时盐水含盐百分比是（　　）

下列加线词语使用有误的一项是 （       ）

    Homework is a problem for students all over the world. As a student, you have a lot of homework to do every day. ____. And it helps you understand important knowledge. Luckily, there're several things you can do to make homework less difficult.

    ____. Write your homework down in your notebook if you need to. Don't be afraid to ask questions about it. Understand why you should do your homework.

    ____. Many schools have study halls. The students can study there. It's more interesting to play with your friends. But the more homework you finish at school, the less you'll have to do that night at home.

    ____. It is difficult to hold your attention for too long. So take some breaks while doing your homework. Taking a 15-minute break every hour is a good idea for most people.

    ____. If you don't finish your homework at school, think about how much you have left. It's a good idea to make a homework plan, especially when you want to enjoy sports or other activities.