a $7-$bit binary word

Select one or more:

a$.$ may be used to represent an unsigned integer in range $0.\mathrm{.}128$

b$.$ is sufficient to store any ASCll character code

c$.$ may be used to encode a text character in the UTF$-8$ code

d$.$ may be used to encode an integer in U$2$ coding in the range $-64.+63$