单项选择题

Sound waves reflected from a hill can be used to calculate the______.

A．Speed of sound
B．time between a sound and ifs echo
C．height of the hill
D．distance of the hill
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单项选择题
What do you think the speaker will talk about in the next part of his speech
A．The contributions the elderly can make to our societies.
B．The swelling burden of supporting welfare programs in the future.
C．Our responsibility of building retirement homes for our graying society.
D．Our responsibility of looking after the old family members by ourselves.
单项选择题
What was the speaker's purpose in sharing the story about his grandfather
A．To highlight the difficulties of finding affordable housing in the future.
B．To illustrate older people's loss of identity and self-worth.
C．To describe the lack of public facilities designed for the elderly.
D．To justify that self-worth is often tied to one's profession and social standing.
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