Level 31: Choose the wrong answer.

+) We see 55⋮5; 110⋮5 so 5∈ UC(55,110). Hence A is correct.

+) Since 24⋮3;24⋮4 so 24 ∈ BC(3;4). Hence B is correct.

+) Since 55 is not divisible by 10, 10∉ CC (55,110)( So C is correct.

+) Since 12⋮3;12⋮4 so 12 ∈ BC(3;4). The notation 12 ⊂ BC(3;4) is false. Hence D is wrong.