system: You are an expert security code reviewer. You will be shown a source code file along with a multiple-choice question listing several function or class names from that file. Your task is to identify which one contains the specified CWE vulnerability.

OUTPUT FORMAT: Respond with the single letter of the correct option, wrapped in \boxed{...}. Example: `\boxed{B}`. Output the boxed letter ONLY -- no explanation, no other text.

user: ```python
import re
from datetime import date
import uuid

''' Contains useful utility functions for our Flask app '''
def get_database_uri_from(env):
    '''
    Use values from the environment to determine a Database URI per the SQLAlchemy schema.
    See https://docs.sqlalchemy.org/en/14/core/engines.html#database-urls for specifics.
    '''

    # SQLite URLs use a local file on disk with no login info
    if env["DB_PROTOCOL"] == 'sqlite':
        return f'sqlite:///{env["DB_NAME"]}'
    
    return f'{env["DB_PROTOCOL"]}://{env["DB_USERNAME"]}:{env["DB_PASSWORD"]}@{env["DB_HOST"]}/{env["DB_NAME"]}'

def validate_email(email):
    '''
    Returns True if email is a properly formatted email address;
    returns False otherwise.
    '''
    return (
        isinstance(email, str)
        and re.search(r'^([a-z0-9]+[\._]?)*[a-z0-9]+@\w+\.\w+$', email) is not None
    )


def get_display_name(email):
    '''Returns the first part of an email as a display name'''
    return email[: email.index('@')]


def get_elapsed_days(startDate, endDate=date.today()):
    '''
    Returns the number of days between the provided start and end dates.
    Defaults to returning the number of days between the start date and today.
    '''
    return (endDate - startDate).days


def append_to_login_bitfield(bitfield, days_since_last_login):
    '''
    Insert (`days_since_last_login` - 1) deactivated bits to the front (most significant) end
    of the existing `bitfield` integer. Insert one activated bit to the very front.
    Returns the updated `bitfield` integer.
    '''
    if days_since_last_login <= 0:
        return bitfield
    
    return bitfield + (1 << (bitfield.bit_length() + days_since_last_login - 1))


def get_credit(login_bitfield):
    '''
    Returns a string representing the amount of monetary credit earned from the given
    series of user logins. Effectively just counts the number of 1s in the integer
    and multiplies it by the amount we credit per day.
    '''
    return 1.0 * bin(login_bitfield).count('1')

def get_or_create(db_session, model, **kwargs):
    '''
    Gets or create an instance of a particular model with the given attributes
    See https://stackoverflow.com/questions/2546207/does-sqlalchemy-have-an-equivalent-of-djangos-get-or-create
    '''
    instance = db_session.query(model).filter_by(**kwargs).first()

    if not instance:
        instance = model(**kwargs)
        db_session.add(instance)

    return instance

def get_random_session_token():
    '''Create a random session token string'''
    return str(uuid.uuid4())

```

Which of the following functions or classes contains a `CWE-1333: Inefficient Regular Expression Complexity` vulnerability?

  A) get_display_name
  B) get_random_session_token
  C) validate_email
  D) get_credit
Answer: C