$3.$ Consider the following set, determine if the answer is true or false. Provide brief explanation for your answer.

A$=(3,4,\{3,4\},\{1,2,3\},5\}$

a$.$ The cardinality of A is $5=$ True

b$.\{3\}$ A

c$.\{1\}$ A

d$.\{1,2,3\}$ A