Consider a recursive function called palindromeR (str) that returns true if a string is a palindrome (reads the same backwards and forwards). What is a valid recursive call for palindromeR? palindromeR (str[1:1]) palindromeR (str) return palindromeR (str) return palindromeR (str [1:1]) None of other selections are valid Consider a recursive function called palindromeR (str) that returns true if a string is a palindrome (reads the same backwards and forwards). What is the time complexity of palindromeR? O(n) None of other selections are valid O(n2) O(n2) O(log(n)) Consider the functions power (base, exp) and betterpower (base, exp) that recursively calculate the value of base raised to exp. def power (b,x): if (x==0): return 1 return b power (b,x1) def betterPower 1(b,x): if (x==0): return 1 if x%2=0 : return betterPower 1(b,x//2) betterPower 1(b,x//2) else: return b betterPower 1(b,x//2) betterPower 1(b,x//2) What is the time complexity of betterpower 1 ? O(log(n)) O(n) O(2n) O(n!) O(n2)