Engines are to machines ______hearts are to animals.

Engines are to machines ______hearts are to animals.
A.as B.that C.what D.which
选C
不是有A is to B (just) as C is to D=A is to B what C is to D

我也觉得a,c都可以,我找了一些外国人对这种题目的看法,
还有几个外国人对于类似问题的回答,分别是：
问题
Twelve is to three ____ four is to one.
A.what
B.as
C.that
D.like
The syllabus "pronounces" A as the correct answer.
答复1
Simple as far as I'm concerned:Twelve is to three as four is to one.
Why?Because the statement is in the form of an analogy,and that's the way analogies are written.Another way it could be written is as follows:
Twelve :three = four :one
However,even though it's written this way,you would still read it,"Twelve is to three as four is to one".
答复2
D should be the answer.However as a spoken answer both B & D would be suitable.
B is a contraction of 'much as' or 'much the same as.'
The argument for D comes from this sentence being a comparrison of two clauses of equivalent proportion (ratio).
答复3
The correct answer is B for the formal British English that TEM 4 is testing although informally and in American English especially,"like" would be good as well.Here "as" is a conjunction indicating comparison as the OED and Michael Swan's Practical English Usage (New Edition,Oxford University Press,1998) both explain.
答复4
Answer is B [as] in grammatical language,A [what] in mathematical language?
答复5
In all my years of taking standardized tests in the U.S.,including the SAT and GRE,the questions have all been written:Twelve is to three AS four is to one.
I don't know how to explain the grammer.
Is it different in the UK or Australia?
答复6
I would use "what" in conversation and "as" for an analogies test.
Conversation example:"Texas is to America what America is to the rest of the world."
Test example:"Light is to dark as tall is to short."