单选题 According to the first paragraph, the ability to feel joy in life is being able to feel__________.

单选题 The author thinks that business cards are ____________ in the digital time.

单选题 People experiencing economical difficulties would generally feel__________.

单选题 Requiring a person's email address is regarded as one of the ____________.

单选题 According to the passage smart phones are ____________.

单选题 Which of the following can help people maintain the ability to feel grateful for life?

单选题 What do you have to do before you can pass your personal information on the smart phone?

单选题 The author thinks the best way of exchanging contact information is by ____________.