简述程序文件的编写项目？

空间中存在着如图所示的竖直方向的匀强电场。已知abcd为一矩形，ab=16cm，ad=30cm。从某实验装置中喷射出的带正电的微粒，质量m=1.0×10^-22kg、带电量q=1.0×10^-16C。微粒以垂直于电场方向的速度v₀=1.5×10⁴m/s，从ab正中间射入电场，最后从c点射出。不计微粒重力。求：⑴ 电场强度的大小和方向。⑵ a、c两点间的电压。

Ben Olsen had great careers as professional players. His story tells a lot about the past, present and future of professional soccer in America.

Ben Olsen was an important part of D.C. United's early success. He was the top new player, or rookie of the year, in 1998. His young professional career reached a high point the next season. D.C. United won the M.L.S. Cup, the league championship（锦标赛）, on the strength（力量） of a Most Valuable Player performance by Olsen. He scored one of two goals for his team in the win against the Los Angeles Galaxy.

Ben Olsen looks back on his score in that championship as his most memorable. "I'd lost a lot of championships before that year, so that was a special game." said Ben Olsen.

Like many top American soccer players, Olsen played overseas. He joined the club Nottingham Forest in Britain. He says different leagues have different styles of play. "Some teams are very fast and athletic. Some teams are a little bit more low pressure on the ball and more skillful players. England has always been known to be a fast and physical league."

Olsen was also a part of the United States World Cup team of 2006. He says playing for his country was something he will never forget. 

Ben Olsen has had five operations for severe ankle（脚踝） injuries. Still, he had one of his best years in 2007. He scored seven goals including a "hat trick"-- three in one game.

Ben Olsen celebrates his third goal in one game against the New York Red Bull in June of 2007

He was recognized for his outstanding play with an M.L.S. Best Eleven award. He accepted the award in a wheelchair after a minor operation became major ankle surgery（外科手术）. Ben Olsen retired after the 2009 season. Today he is an assistant coach with D.C. United.

小题1:When did Ben Olsen begin to win championship?

A． In 1998

B．Next season

C．In 1999

D．In 2006小题2:What does the underlined word ‘rookie’ mean in this sentence?

A．Success

B．New player

C．professional career

D．championship小题3:According to the passage, which of the following is true?

A．Ben Olsen has a deep love for his country

B．Ben Olsen scored three goals in 1999

C．Top American soccer players never played oversea

D．He scored ten goals in 2007小题4:What do you think is the best title for the passage?

A. Ben Olsen—the best soccer player

B. Ben Olsen’s professional career

C. Ben Olsen and D.C. United

D. An introduction to Ben Olsen

掉发的因素有哪些？

简述财政公共选择的概念与特点。