In fully associative cache, search for a block is simultaneously done for all entries based on the Tag.
So no need for indexing ( neither set nor line no).
Total size, tag bits + block offset bits = 32
Block size = 16 B = $2^4$B
So we require 4 bits to address a block. Thus, tag bits = 32 - 4 = 28
Ans D) 28 and 0 bits