(1) x = 12u, where u is an integer --> x=12ux=12u --> 12u=8y+1212u=8y+12 --> 3(u−1)=2y3(u−1)=2y --> the only thing we know from this is that 3 is a factor of y. Is it GCD of x and y? Not clear: if x=36x=36, then y=3y=3 and GCD(x,y)=3 GCD(x,y)=3
but if x=60x=60, then y=6y=6 and GCD(x,y)=6 --> two different answers. Not sufficient.
(2) y = 12z, where z is an integer --> y=12z --> x=8∗12z+12 --> x=12(8z+1).
So, we have y=12z and x=12(8z+1). Now, as z and 8z+1 do not share any common factor but 1 (8z and 8z+1 are consecutive integers and consecutive integers do not share any common factor 1. As 8z has all factors of z then z and 8z+1 also do not share any common factor but 1).
Thus, 12 must be GCD of x and y. Sufficient.
There's also the brute force method, which doesn't take that much time here.
Amy's grade is 90th percentile, meaning that she outperformed 90% of her classmates. That means that she outperformed 72 of her classmates.
She also outperformed 81 of the students in the other class (note: not 80, because Amy herself is not in the other class).
This means that she outperformed 72 + 81 = 153 of the combined 180 students in the two classes.
Since 153/180 = 0.85, she outperformed 85% of the students in the combined pool, putting her in the overall 85th percentile.
1.the two MAIN VERBS in the sentence are "call" and "attract".
2."instead of" is generally restricted to NOUNS.
"rather than" can be used for essentially ANY part of speech at all.
3.SUBJECT + ACTIVE VERB + BY + NOUN is generally incorrect.**
SUBJECT + ACTIVE VERB + BY + VERBing is generally correct, if "VERBing" is the method or process by which the ACTIVE VERB is carried out.
SUBJECT + PASSIVE VERB + BY + NOUN is an absolutely fundamental form, if the NOUN is the thing/person that did the action to the SUBJECT.
1. if the subject of a verb is unknown or irrelevant, use the passive voice.
2.In the problem at hand, the original sentence, along with answer choices B and D, indicate that scientists removed "a synthetic growth hormone" from cadavers. This is nonsensical, as something synthetic, by definition, does not come from a natural source. Thus, A, B, and D can be eliminated based on their lack of clarity.
排除掉ABD，CE里面比最优，E: "before learning"修饰的是scientists,和主句主语矛盾。
'to be sighted' is better for at least two reasons.
(1) 'first NOUN to be VERBed' is generally the preferred form in discussing the results of human efforts/actions/interference/perception/etc., while 'first VERBed NOUN' is generally used to indicate inherent qualities of the noun.
for instance, the following sentence is preferred:
henry bishop was the first musician to be knighted by a british monarch. --> knighting is performed by humans
the following is NOT preferred:
henry bishop was the first knighted musician in britain. --> this makes it seem as though being 'knighted' is an inherent quality with which henry bishop was born, or that he acquired it naturally/accidentally in some other way
(2) the word 'sighted' means 'having the sense of sight', so this sentence also contains the amusing alternative interpretation of referring to a pulsar that can actually see.
(e) "what the effects" is ungrammatical.
also, in constructions of this sort, "what" is generally redundant / unnecessary; it's better merely to say "to investigate X" rather than to say "to investigate what X is" (or other such wordy construction).
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mine和produce之间存在逻辑关系，并非并列！