Problem: Geological history of Earth:

Earth was initially molten due to extreme volcanism and frequent collisions with other bodies. Eventually, the outer layer of the planet cooled to form a solid crust when water began accumulating in the atmosphere. The Moon formed soon afterwards, possibly as the result of a Mars-sized object with about 10% of the Earth's mass impacting the planet in a glancing blow. Some of this object's mass merged with the Earth, significantly altering its internal composition, and a portion was ejected into space. Some of the material survived to form an orbiting moon. Outgassing and volcanic activity produced the primordial atmosphere. Condensing water vapor, augmented by ice delivered from comets, produced the oceans.

How does the mass of the moon compare to earth?
---
A: about 10% of the Earth's mass

Problem: Department store:

Since the opening policy in 1979, the Chinese department stores also develops swiftly along with the fast-growing economy. There are different department store groups dominating different regions. For example, INTIME department store has the biggest market presence in Zhejiang province, while Jinying department stores dominate Jiangsu Province. Besides, there are many other department store groups, such as Pacific, Parkson, Wangfujing,New World,etc., many of them are expanding quickly by listing in the financial market.

What ended the influx of Chinese department stores?
---
A: unanswerable

Problem: Paper:

The oldest known archaeological fragments of the immediate precursor to modern paper, date to the 2nd century BC in China. The pulp papermaking process is ascribed to Cai Lun, a 2nd-century AD Han court eunuch. With paper as an effective substitute for silk in many applications, China could export silk in greater quantity, contributing to a Golden Age.

What material did paper not replace upon its invention?
---
A: unanswerable

Problem: BeiDou Navigation Satellite System:

The original idea of a Chinese satellite navigation system was conceived by Chen Fangyun and his colleagues in the 1980s. According to the China National Space Administration, the development of the system would be carried out in three steps:

What idea did Chen Fangyun come up with in 1924?
---
A:
unanswerable