Take here A as epsilon
C) By shifting rule (r1.r2)*.r1 = r1(r2.r1)*.
(s*ttt)*s* and s*(ttts*)* are defining same language
B) A +0(0+1)* + (0+1)* 00(0+1)* defining the language with atleast 2 zeroes but ((1*0)*01*)* it is not ( 10 is not acceptable)
A) p(pp)*( A + p)q + q for this language L ={q,ppq,pppq,.....}. p*q for this language L={q,pq,ppq,…} those two are not equal.
So c only have the pair of regular expression s define the same language