阅读下列短文，从每题所给的四个选项（A、B、C和D）中，选出最佳选项。
A
Interested in learning a new language but don't know where to start? Here are the best online language learning courses we've put together for your reference.
Rosetta Stone
Price: $7.99 per month-$199 one-time payment
Number of languages: 28
Rosetta Stone has long been known as the go-to service for new language learners. It offers lessons that are short enough to complete each day, but long enough to actually get something out of. Rosetta Stone's interface is generally easy to use, and its lessons include reading, writing, speaking and listening, all in one lesson. You can also choose to subscribe to a monthly payment or purchase a lifetime license.
Duolingo
Price: Free-$6.99 per month
Number of languages: 36
Duolingo has risen as a serious competitor to Rosetta Stone over the past few years. The service is perhaps best known for its Android and iOS apps, and those apps are available for free — which makes it easy to practice your chosen language without having to make a serious commitment. Alternatively, you can sign up for Duolingo Plus, which removes ads, offers offline courses, and more. Many consider Duolingo to be better for those who want to practice a language rather than learn from the very beginning.
Babbel
Price: $6.95 per month-$12.95 per month
Number of languages: 14
Looking for a service to challenge your language-learning skills? Babbel may be the way to go. Babbel is excellent at teaching phrases and words that you'll actually use on a day-to-day basis. The service is also relatively cheap, so if you're unsure if you want to commit to learning a new language yet, the low subscription prices ensure you don't have to make a huge commitment.
Memrise
Price: $6.67 per month-$119.99 one-time payment （extra 10% off before July）
Number of languages: 16
If you learn best through repetition and flashcards, then Memrise may be the service for you. It's relatively inexpensive, making it easier to sign up. Memrise isn't necessarily the service for those who want to learn a language from scratch, but it's a great learning aid, and good for those who already have a foundation in language-learning.
21. What is TRUE about Rosetta Stone?
A. It covers the widest range of languages.
B. It is intended for high-level learners.
C. It helps improve multiple language skills.
D. It offers a one-month free trial.
22. Which courses are more suitable for people with certain basis?
A. Rosetta Stone and Memrise.
B. Duolingo and Memrise.
C. Babbel and Rosetta Stone.
D. Babbel and Duolingo.
23. How much should you pay if you want to get a lifetime access to Memrise in May?
A. $119.99.
B. $129.50.
C. $107.99.
D. $199.
