GC scan for pointers

[Gerald Jansen via Digitalmars-d-learn]

I've studied [1] and [2] but don't understand everything there. 
Hence these dumb questions:

Given

   enum n = 100_000_000; // some big number
   auto a = new ulong[](n);
   auto b = new char[8][](n);
   struct S { ulong x; char[8] y; }
   auto c = new S[](n);

will the large memory blocks allocated for a, b and/or c actually 
be scanned for pointers to GC-allocated memory during a garbage 
collection? If so, why?

[1] 
http://p0nce.github.io/d-idioms/#How-the-D-Garbage-Collector-works
[2] http://dlang.org/garbage.html