Sentence Correction

Hi Guys - I know this has already been discussed but I haven't been able to understand the OA yet.
Could someone please provide some expert opinion ?

After suffering the effects of several tsunamis, the residents of a Japanese city built a wall on their coast over forty feet high and a mile long, a way to protect the city against another disaster.

a. a way to protect
b. in efforts to protect
c. protecting
d. to protect in one way
e. in order to protect

OA C[/u]

The choices a,b and d can be eliminated right away.

the fight is between c and e.

between the two both seem to be grammatically correct.

c- protecting modifies the complete cluase before the comma.

e -- comma followed by "in order to protect" is not clear as to wht is being used to protect as the "wall" is far far away.

hope it helps.