select one or more:

a$.$ Building T$1$ requires a backtrack search algorithm as a Greedy method doe guarantee the optimality of the constructed Huffman tree.,

b$.$ According to T$1,$ comma $(",")$ is the least frequent character in $F_1.$

c$.$ According to T$1,$ the characters $($colons$,$ spaces, newlines, commas, and coded using different number of bits.

d$.$ Building T$1$ is done using a Greedy method with complexity NlogN$(1)$ number of characters$).$

e$.$ According to T$1,$ characters $"1"$ and $"7"$ are both coded using $4$ bits.