19)
2 answers:
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Answer:
C
Explanation:
A. Since
B. Because
C. Although
D. For example
<em>Zebra mussels have been known to have a lifespan of six or seven years in the past but recent discoveries have shown that their average lifespan now ranges between one to two years. Hence, the correct word to fill in the gap would be 'Although'. </em>
<em>The correct option is C</em>
