题目内容：

What do you use to unlock your cellphone? A password? A fingerprint? Or simply a glance?

On September 12, 2017, Apple introduced its iPhone X, which has an eye-catching feature—Face ID.

With Face ID, Apple says, you can unlock your new iPhone by just looking at it. It is powered by a so-called TrueDepth camera system built into the front of the iPhone X.

When the camera system sees a person’s face, it uses 30,000 unseen dots to “map” the shape and outline of the face. A mathematical model of the face will then be created and stored in the phone.

The next time the person looks at the iPhone X, the same dots are mapped onto his or her face and compared to the stored model. If the two match, then the phone unlocks. This happens in less than a second.

Apple says the system is smart. If you change your hairstyle, put on sunglasses or makeup, or use the phone in the dark, Face ID still works.

Although the technology sounds fancy, there are still concerns. For example, will Face ID work for twins?

According to Apple, the chance of others to unlock your iPhone X using Face ID is one in a million. Face ID can tell the difference between twins, but the error rating（出错率）rises. So one would need to set a password then.

Apple also emphasizes that Face ID only unlocks when you stare at it. It is what Apple calls “attention aware”. So the phone won’t unlock if you are just glancing at the phone for the time. It won’t work either if someone puts the phone at your sleeping face or your photo.

1.Face ID helps iPhone X users to ________.

A. get their phones more eye-catching

B. make the phone camera powerful

C. unlock their cell phones quickly

D. create and store their face model easily

2.How does the camera system of Face ID work?

A. It compares the face model with the user’s face later.

B. It remembers the users’ faces by taking their pictures.

C. It uses a map to store face models of its users for use.

D. It matches the users’ faces with dots in the system.

3.The iPhone X users may not unlock their phones when ________.

A. they wear makeup    B. the users are twins

C. they change the hairstyles    D. they use it without lights

4.What is the best title of the text?

A. The introduction of the iPhone X

B. The features of the iPhone X

C. The iPhone X recognizes a face

D. Unlock the iPhone X by a stare.