根据中文提示写出单词或词组，使句意完整、正确。
–How many _________(邮票) have you collected?
–More than 500.2.
–Excuse me. How many times have you ever been to Europe?
–              (两次).
We should try our best to ____________(保护) the wild animals.
There are _________________(至少) 5000 workers in that factory.
The radio_______________(发明) by Guglielmo Marconi in 1895.