[单选题]设R、S、T是集合A={a，b，c}上的关系，定义如下：R={<a,b>}S={<b,b>,<b,c>}T={<b,c>}计算（R◦S）U（R◦T）=（ ）。
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2023-11-01 15:11:12|
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[单选题]设R、S、T是集合A={a，b，c}上的关系，定义如下：R={<a,b>}S={<b,b>,<b,c>}T={<b,c>}计算（R◦S）U（R◦T）=（ ）。
A.{< a ,c > }
B.{< a ,b >,< b ,b >,< b ,c >}
C.{< a, b >, < a,c > ,< b, b >, < b,c > }
D.{<a,b>,<a,c>}
A.{< a ,c > }
B.{< a ,b >,< b ,b >,< b ,c >}
C.{< a, b >, < a,c > ,< b, b >, < b,c > }
D.{<a,b>,<a,c>}
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