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.Have you ever unlocked a shared bike? Have you ever ordered a meal online? Have you ever enjoyed watching the short- form videos on the Internet? Well, if no one had invented the cell phone, none of these would have been possible.
Luckily, someone did invent the cell phone. That person is Martin Cooper, and he did that 51 years ago, in 1973.
Cooper used to work for Motorola. In the 1970s, the company was competing with AT&. T, a larger company, to make a cell phone system. Cooper didn't think Motorola's product was good enough. He didn't like AT&T's idea of a car phone, either. The man had a new idea. He wanted to make it possible for people to talk on their phones anywhere.
It took Cooper and his team 90 days to design the world's first cell phone. The product was called Dyna TAC. People could talk on it for 25minutes before its battery（电池）died. The phone's short battery life wasn't a big problem, Cooper once joked. Why? Well, the phone was too heavy（1,100 grams）to hold in hand for more than 25minutes!
On 3 April, 1973, Cooper made the world's first public cell phone call. He called Joel Engel, an AT&T manager. Cooper told Engel, "I'm calling you on a cell phone. It's a real, handheld cell phone." On the other end of the line, there was only silence.
Cell phones have changed a lot since that first call. They're much smaller and can do many more things. Cooper, now 96, is surprised at the progress.
But the man has also kept thinking about life in the future. "Keep learning all your life," he says, "or you'll lose the ability to learn-- that would be terrible!"
