Question: Read this and answer the question

The state of California was admitted to the United States in 1850. That same year San Diego was designated the seat of the newly established San Diego County and was incorporated as a city. Joshua H. Bean, the last alcalde of San Diego, was elected the first mayor. Two years later the city was bankrupt; the California legislature revoked the city's charter and placed it under control of a board of trustees, where it remained until 1889. A city charter was re-established in 1889 and today's city charter was adopted in 1931.

Who controlled San Diego's charter for 2 years after it was revoked by California legislature?
Answer: a board of trustees
Question: Read this and answer the question

CD-R recordings are designed to be permanent. Over time, the dye's physical characteristics may change causing read errors and data loss until the reading device cannot recover with error correction methods. The design life is from 20 to 100 years, depending on the quality of the discs, the quality of the writing drive, and storage conditions. However, testing has demonstrated such degradation of some discs in as little as 18 months under normal storage conditions. This failure is known as disc rot, for which there are several, mostly environmental, reasons.

What can cause sudden disc degradation?
Answer: disc rot
Question: Read this and answer the question

Because the electron mobility is higher than the hole mobility for all semiconductor materials, a given bipolar n–p–n transistor tends to be swifter than an equivalent p–n–p transistor. GaAs has the highest electron mobility of the three semiconductors. It is for this reason that GaAs is used in high-frequency applications. A relatively recent FET development, the high-electron-mobility transistor (HEMT), has a heterostructure (junction between different semiconductor materials) of aluminium gallium arsenide (AlGaAs)-gallium arsenide (GaAs) which has twice the electron mobility of a GaAs-metal barrier junction. Because of their high speed and low noise, HEMTs are used in satellite receivers working at frequencies around 12 GHz. HEMTs based on gallium nitride and aluminium gallium nitride (AlGaN/GaN HEMTs) provide a still higher electron mobility and are being developed for various applications.

What is the common application of GaAs?
Answer:
high-frequency applications