[quote="Bunuel"]A journalist recently noted that the Stanford Linear Accelerator Center superficially resembles the pipe-filled basement of a large apartment building,
each pipe a conduit not for water, but for electrons traveling through it at near-light speed.
A.
each pipe a conduit not for water, but for electrons traveling through
itB. each pipe a conduit not for water, but for electrons traveling through
themC. all the pipes a conduit not for water, but for electrons traveling through
themD.
all the pipes a conduit not for water, but for electrons traveling through it
E. every pipe a conduit not for water, but for electrons traveling through
themThe resemblance of Stanford Linear...is compared to that of pipe, we need a singular entity 'pipe' for comparison and not plural 'them' so options B, C, and E are out. Out of A and D again we are only comparing with one entity i.e pipe, so the usage of 'All' is incorrect.