8051单片机复位后，P0-P3口的初始值为（ ）。

A. 0x00
B. 0xFF
C. 0x07
D. 0x0F

若MCS-51单片机使用晶振频率为12MHz时，其复位电平持续时间应该超过（ ）。

A. 2μs
B. 4μs
C. 8μs
D. 1ms

8051单片机选择内部时钟方式，已知外接晶振频率fosc=6MHz，则单片机的振荡周期为（1）微秒，机器周期为（2）微秒。（1）写成分数形式，比如“二分之一“写成“1/2”

与微型计算机系统不同，8051单片机的程序存储器和数据存储器在物理上各自独立，这种结构称为（1）；8051单片机片内程序存储器大小为（2）Byte，片内数据存储器大小为（3）Byte；在访问外部存储器时，P2口和P0口作为地址总线，最大可寻址（4）Byte；其中（5）口分时地作为数据总线。

一、单选题（共2题，50分）1、which is the better translation of the following sentence?在悉尼的郊区，有五周的时间尝试无车的生活方式，这令我们激动不已。

A. In sydney suburbs, there is 5-week lifestyle experiment of living without a car, we are excited about it.
B. We are excited about the 5-week lifestyle experiment of living without a car in the suburbs of Sydney.

2、瑞典哥德堡丢了一个六个月大的婴儿，然后全城警察出动，调用直升机和所有警犬全城搜捕，最后，婴儿在丢失两个小时后找到。How will you write it in English?

A six-month-old baby has been found, just over two hours after her disappearcance in Gothenburg.Earlier the police called in extra resoures, including police dogs and helicopters to help with the search efforts.
B. In Gothernburg, a six-month-old baby has been lost. Then all the police in the city went out to reseach her with police dogs and helicopters to help with the search efforts. Finally, the bay girl was found two hours later.

二、多选题（共2题，50分）1、Please choose the right sentences from the followingfour sentences.

A. Since I get my smart phone, I spend too much time texting my friends , I hardly ever send e-mails anymore.
B. Since I get my smart phone, I hardly ever send e-mails. Instead, I spend too much time texting my friends .
C. Hardly do I email my friends since I get my smart phone
D. SinceIget my smart phone, I don't e-mail my friend, I spend too much texting them.

2、In the following four choices A, B, C, D, which are good translations of the sentence"很多家长忙于工作，忽视了与孩子的沟通，这可能会导致孩子出现心理问题。"

A. Many parents spend most of their time at work, neglect the interaction with their children, it may lead to children's psychological problems.
B. Many parents spend most of their time at work and neglecting the interaction with their children, it may lead to psychological problems.
C. Many parents spend most of their time with their work and ignore the itneraction with chilidren, which leads to psychological problems with children.
D. If many parents spend most of their time at work and neglect the interaction with their children, children may have psychological problems.

列举TivaWare软件库中的外设驱动库主要组成部分。

PWM是什么意思？PWM的主要用途是什么？PWM有什么优点？