The two sentences that describe a cause and effect relationship are:
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Because the wind was blowing furiously, our umbrella managed to be carried off down the street. (The cause is the wind blowing furiously, and the effect is that the umbrella was carried off.)
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Alice opened her novel, but because her bookmark fell out she was unable to remember her page number. (The cause is the bookmark falling out, and the effect is being unable to remember the page number.)