Can explain to me why the answer is asp. Can u explain each line

examstudy 1.py - C:/Users/skhan/Desktop/examstudy 1.py (3.7.2) File Edit Format Run Options Window Help def isPrefix (a,b): prefix-' index-0 for letter in b if indexlen (a): elif a[index]b[index]: else: return a return prefix prefix += b index+1 return prefix wordo-'asp wordl-'asparagus' print (isPrefix(wordo, word1))