A special Japanese green tea called genmai-cha contains brown rice and

(A) A special Japanese green tea called genmai-cha contains brown rice and is considered as a delicacy fit for a gourmet by most Japanese, though it is virtually unavailable outside Yokohama. -- it has no clear referrant..it can refer to green tea or brown rice..
(B) Considered to be a delicacy fit for a gourmet by most Japanese, genmai-cha is a special green tea that contains brown rice, virtually unavailable outside Yokohama. -- virtually unavailable outside Yokohama modifies brown rice, hence, incorrect
(C) A special Japanese green tea called genmai-cha contains brown rice and is considered a gourmet delicacy by most Japanese, though it is virtually unavailable outside Yokohama. -- same as A.
(D) Most Japanese consider genmai-cha, a special green tea which contains brown rice, as a delicacy virtually unavailable outside Yokohama. -- correct..i won't say free of errors but best among the rest..
(E) Though virtually unavailable outside Yokohama, most Japanese consider genmai-cha, a special green tea that contains brown rice, a gourmet delicacy. -- incorrect modifier , Though virtually unavailable outside Yokohama modifes most japanese..

it, in A and C, refers to A special Japanese green tea. In subordination the common rule is that the subject pronoun refers to the subject of the other clause.

Here is an example from the OG

while depressed property values can hurt some large investors, they are

Here they refers to depressed property values.

Hi There,

The pronoun "it" in choice C grammatically and logically refers to "A special Japanese green tea". Pronoun "it" is the subject of the dependent clause that starts with "though". Because "it" is at the subject place, grammatically it will refer to teh subject of the preceding clause. The subject of the preceding independent clause is "A special Japanese green tea". Logically also, "it" refers to genmai-tea as the contrast presented by "thpugh" is about this tea only. Although the tea is considered "delicacy", it is only available in Yokohama.

Hope this helps.
Thanks.
Shraddha

A special Japanese green tea called genmai-cha contains brown rice and is considered as a delicacy fit for a gourmet by most Japanese, though it is virtually unavailable outside Yokohama.
(A) A special Japanese green tea called genmai-cha contains brown rice and is considered as a delicacy fit for a gourmet by most Japanese, though it is virtually unavailable outside Yokohama.
(B) Considered to be a delicacy fit for a gourmet by most Japanese, genmai-cha is a special green tea that contains brown rice, virtually unavailable outside Yokohama.
(C) A special Japanese green tea called genmai-cha contains brown rice and is considered a gourmet delicacy by most Japanese, though it is virtually unavailable outside Yokohama. lets keep it,though using it is doubtful ,but no other error
(D) Most Japanese consider genmai-cha, [a special green tea which contains brown rice], as a delicacy virtually unavailable outside Yokohama. remove bracketed part and then read. "consider as" is wrong
(E) Though virtually unavailable outside Yokohama, most Japanese consider genmai-cha, a special green tea that contains brown rice, a gourmet delicacy. misplaced modifier."most japanese" are not virtually unavailable it is green tea thats virtually unavailable.

So the only option that best fits is option C.

“Considered - as” or “considered - to be” are incorrect IDIOMS

C - Correct

In option C ,
Why has a comma been put before "Though" ?

D distorts the meaning. The Japanese don't "consider" that the tea is unavailable outside Yokohama. It is a fact that the tea is unavailable outside Yokohama.

C "it" refers to the Japanese green tea