“Please speak up a bit more, Jason. You’re hardly loud enough to be heard from the back”, the teacher said.
Giải chi tiết:
Population growth rates vary among regions and even among countries within the same region.
Biogas can be utilized for electricity production, cooking, space heating, water heating and process heating.
Around 150 B.C. the Greek astronomer Hipparchus developed a system to classify stars according to brightness.