3-4-21

poppyxams

21. During construction of the Quebec
            Bridge in 1907, the bridge’s designer, Theodore Cooper, received word that the suspended span being built out from the bridge’s cantilever was deflecting downward by fraction of an inch. Before he could telegraph to freeze the project, the whole cantilever arm broke off and plunged, along with seven dozens workers, into the St. Lawrence River. It was the worst bridge construction disaster in history. As a direct result of the inquiry that followed, the engineering “rules of thumb” by which thousands of bridges had been built went down with the Quebec Bridge Twentieth-century bridge engineers would thereafter depend on far more rigorous applications of mathematical analysis.

Which one of the following statements can be properly inferred from the passage?

(A) Bridges built before about 1907 were built without thorough mathematical analysis and therefore, were unsafe for the public to use

(B) Cooper’s absence from the Quebec
            Bridge construction site resulted in the breaking off of the cantilever.

(C) Nineteenth-century bridge engineers relied o their rules of thumb because analytical methods were inadequate to solve their design problems.

(D) Only a more rigorous application of mathematical analysis to the design of the Quebec
            Bridge could have prevented its collapse

(E) Prior to 1907 the mathematical analysis incorporated in engineering rules of thumb was insufficient to completely assure the safety of bridges under construction.

KEY:E

D is better for me.

E says "Prior to 1907...was insufficient to completely assure the safety of bridges under construction", but one bridge collapsed doesn't mean all other bridges must fail too. Probably some other bridges are easier to construct so 'the mathematical analysis incorporated in engineering rules of thumb' was good enough.   'Bridges under construction' is a too much broader notion used here. 

And I don't see anything wrong with D.

Why is that?

MANY THANKS!

 

dphxmg

According to D, the lack of a more thorough mathematical analysis was the only reason for the collapse of the Quebec Bridge. I can't see that from the stem.

poppyxams

"ONLY..." represents a surfficient condition, right?

I thought ONLY was the necessary one. ;( 

Is there a difference between "if only" and "only if"? I'm very confused about.

THANKS.