B4

The Huang He, or Yellow River, in China is called “China’s Sorrow” by the Chinese themselves. Since long ago, flooding has been a serious problem.
(present perfect, т.к. с тех пор и до сих пор)

BE

B5

The worst, most sorrowful flood on record happened in 1931.
(bad – worse - the worst)

 BAD

B6

The waters began to rise in July, and by November of that year, more than 40,000 square miles had been flooded, leaving 80 million people homeless.
(Participle I, “оставляя”, подходит по смысловому контексту)

 LEAVE

B7

Once there lived a rabbit and a tortoise. The rabbit challenged the tortoise to have a race with him. The tortoise agreed and they started the race.
(с ним)

 HE

B8

The rabbit ran faster than the tortoise, and in a few minutes he was near the crossing line. He couldn’t see the tortoise, so he decided to rest for a while till the tortoise arrived and then he would quickly cross the line.
(степень сравнения)

 FAST

B9

The rabbit lay down under a tree and soon he was asleep. When he awoke, he saw that the tortoise had crossed / was crossing the line.
(past perfect, он увидел, что черепаха пересекла линию до того, как он проснулся.
past continuous, он увидел, что черепаха пересекала линию в тот момент, когда он просыпался)

CROSS

B10

The tortoise won the match, showing that it’s more important to be steady and active than to be fast.
(past simple, т.к. действие произошло в определённый момент в прошлом)

WIN