题干

在DNA分子双螺旋结构中,腺嘌呤与胸腺嘧啶之间有2个氢键,胞嘧啶与鸟嘌呤之间有3个氢键。现有四种DNA样品,根据样品中碱基的百分含量判断最有可能来自嗜热菌(生活在高温环境中)的是(  )

A:含胸腺嘧啶32%的样品

B:含腺嘌呤17%的样品

C:含腺嘌呤30%的样品

D:含胞嘧啶15%的样品

上一题 下一题 0.0难度 选择题 更新时间:2019-05-30 08:53:10

答案(点此获取答案解析)

B

同类题4

七选五

    Fun doesn't have to be expensive

    Everyone likes to have fun, but not everyone has much money to spend. Here are some free or cheap ways to enjoy yourself.

    Go outside

    Going outside in good weather can be a lot of fun if you don't want to stay at home. ____ If you live in a city, you can go window-shopping. Or you can explore an old part of town and admire the buildings.

    Try a hobby

    While you're out, take pictures of things you find. Planning and taking pictures can make you aware of the beauty all around you. Photographic equipment can be expensive, but it doesn't have to be. You probably already own a camera or a cell phone that can take pictures. Other creative hobbies can also be done with basic materials. ____

    Find an event

    Libraries often hold free public events. ____And while you're there, borrow a book or movie for free. Museums and universities also hold free events.

    If you can't find a free event, you can volunteer at an event that requires tickets. People who organize concerts and plays need help.____ Sometimes they reward volunteers with free tickets.

    Meet a friend

    Relationships are often the best things in life. ____ For example, invite a friend for a walk, an event or a time working on your hobby. Hosting doesn't have to be difficult. If your friend comes in the afternoon, you don't have to serve a meal. You can sit and talk, play board games or card games or watch a movie together.

A. A friend in need is a friend indeed.

B. Stop by one to find out what's going on.

C. Hike or bicycle with a friend on a nearby path or in a park.

D. Whatever you do, find a friend to share it with.

E. It's a good idea to stay at home to watch a movie.

F. You can set up or take down chairs or greet visitors.

G. Drawing and writing require nothing more than a pencil and paper.