Prob. $1\mathrm{.}7.$

For your convenience, the ciphertext in Problem $1\mathrm{.}5$ is given below:

NTCGPDOPANFLHJINTOOFITOVJHJCTMMHIHEMTCPFDWTSOFSHTOGFWTE

TTJJTBTOOFSZOVEOCHCVCHPJHOCGTOHNQMTOCNTCGPDCGFCSTQMFBO

FBGFSFBCTSHJCGTQMFHJCTYCXHCGFAHYTDDHAATSTJCBGFSFBCTSHJC

GTBHQGTSCTYCCGHONTCGPDQSTOTSWTOCGTMTCCTSASTRVTJBZHJCGQ

MFHJCTYCFJDOPPJTBFJOTFSBGAPSCGTQMFHJCTYCASPNFIHWTJBHQGT

SCTYCEZBPNQFSHJICGTASTRVTJBZPATFBGMTCCTSFIFHJOCCGTLJPXJ

BPNNPJASTRVTJBZHJCGTVJDTSMZHJIMFJIVFIT

a$.$

T in the cipher text corresponds to E in the plain text

b$.$

F in the cipher text corresponds to A in the plain text

c$.$

H in the cipher text corresponds to I in the plain text

d$.$

Suppose you have obtained a partial deciphered text in the first part of the cipher text as follows: "Methods of making messages unintelligible to adversaries have been necessary. Substitution is the simplest method that replaces a character in the plaintext with a fixed different character in the ciphertext." Then some the rest of the cipher text is: "This method preserves the letter frequency in the plaintext"

e$.$

All of the above

f$.$

None of the above

g$.$

a and c