West Indies is a Region, not a country (but it used to be a federation: until 1962, when Queen Elisabeth was the head of this country)
Jamaica IS in the West Indies.
Guyana isn't, but sometimes gets included in it anyway- for example for sports organisations.
Belize is in Central America, and it is NOT in the West Indies.
France, Switzerland, Netherlands
The right answer is "Different age groups are tested at the same time". This type of research is known as A Cross-Sequential Design. These investigations have a cross-sectional and longitudinal, involves analyzing a group of people of different ages (For example 10, 20, 30 and 40 years) over time (For example, for 40 years), this in order to study human development in a particularly long period of life.
I hope my answer can help you.
The first person in space was Yuri Alekseyevich Gagarin, the space rocket, Vostok 1, that sent Yuri into space was manufactured by Energia,