Is considered/regarded to be unidiomatic??? Before the

Is considered/regarded to be unidiomatic???

Before the 17th century, meancholy was regarded to be a disease caused by an excess of black bile in the body and one characterized by delusions, hysteria, distemper, and paralysis.
A..
B. to be adisease, one caused by an excess of black bile in the body and
C. a disease, an excess of black bile in the body caused it, and it was
D. as a disease, being caused by an excess of black bile in the body and
E. as a disease caused by an excess of black bile in the body and

==>E is obviously the best choice, but I thought regarded "to be" was unidiomatic and should be "regarded" + subject like (C), although (C) is awkard and "it" has no referent..

When first introduced into North America, the tomato was regarded that it was poisonous and was planted only as an ornament.
A.
B. considerd to be poisonous
C. regarded as being poison
D. considered poisonous
E. regarded to be poisonous

==> in this case the answer is D...so how do the 2 questions compare?? when do you use "to be"???
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