Which snippet provides a suitable implementation for _normalize_idx in a list implementation, in order to support both negative and positive indexes?

def _normalize_idx(self, idx):

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return nidx

(a) nidx += len(self)

(b) nidx = -idx

if nidx < 0:

nidx += len(self)

(c) nidx = idx

if nidx < 0:

nidx += len(self)

(d) nidx = idx

if nidx < 0:

nidx += len(self)

else:

nidx -= len(self)

def __add__(self, other):

"""Implements `self + other_array_list`. Returns a new ArrayList instance that contains the values in this list followed by those of other."""

assert(isinstance(other, ArrayList))

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(a) self.extend(other) return self

(b) nlst = ArrayList() nlst.extend(self) nlst.extend(other) return nlst

(c) return self + self.extend(other)

(d) return self + other

Which snippet correctly implements remove_first in an array-backed list, given that the underlying data storage mechanism is a ContrainedList (as provided in the ArrayList assignment)? def remove_first(self):

Removes and returns the first element in the list.

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return val

(a) val = self.data.pop(0)

(b) val = self.data[0] del self.data[0]

(c) val = self[0] del self.data[len(self.data)-1]

(d) val = self[0] del self[0]