B4

Modern world of sports knows many kinds of gymnastics. One of them, rhythmic gymnastics grew out of modern gymnastics and the Swedish system of free exercise in the 19-th century.
(past simple, действие произошло тогда, в прошлом. grow - grew)

 GROW

B5

It was called 'aesthetic gymnastics' as the students could express feelings and emotions through body movement. It combined elements of ballet, gymnastics, and theatrical dance.
(could – прошедшая форма от can)

 CAN

B6

Young women exercised to music, moving from simple calisthenics to more energetic activities. A growing number of men are participating in this kind of sport now.
(ед. - мн. число, woman – ед.ч. women-мн.ч.)

 WOMAN

B7

In the 1880s in Switzerland various exercises to music were created. They were designed to give grace of movement, and a much better pose.
(степень сравнения)

 GOOD

B8

A degree of difficulty for each movement was developed by the European Sport Association after the World War I. So all the elements were graded accordingly.
(past simple passive, она была разработана, а не разработала что-то сама)

DEVELOP

B9

In 1906 rhythmic gymnastics was introduced to North America, but the sport didn’t gain / did not gain much popularity.
(past simple, событие произошло в опредёленное время в прошлом)

 NOT GAIN

B10

Ten European countries took part in the first world championship, held in 1973 in Budapest, Hungary. The United States did not begin competing in the biennial world championship until 1973.
(past simple, событие произошло в опредёленное время в прошлом)

 TAKE