Assume that t is an object of class Test, which has member functions a(), b(), c() and d(). If the functions a(), b() and c() all return references to an object of class Test (using the dereferenced this pointer) and function d() returns void, which of the following statements will not produce a syntax error:

a. t.a().b().d();
b. a().b().t;
c. t.d().c();
d. t.a().t.d();

a. t.a().b().d();