All cars that are not registered will be towed to the nearest impound lot.
Identify the relative clause

The relative clause for the statement is “defining relative clause”

Explanation:

A relative clause primarily has a subject along with a verb, but would not stand alone as a complete sentence, hence would have an adjective to be able to give more information about the sentence.

A defining relative clause is one which is well defined as it provides answer to questions such as  “which, where, how”.  

Hence the above statement is a “defining relative clause”.

each morning i wrote my name

on the dusty cabinet, then crossed

the dining table in script, scrawled

in capitals on the backs of chairs,

practicing signatures like scales

while mother followed squirting

linseed from a burping can

i would believe it would be b., the author wants to draw the reader deeper into the experience