def reveal(ch, answer):
    """
    This function will reveal the positions of the letter that
    is in the answer.
    :param ch: str, the characters that are in the answer
    :param answer: str, the word to be guessed
    :return: str, the revealed word after each guessing
    """
    ans = ''
    for i in range(len(answer)):
        for base in ch:
            if answer[i] == base:
                ans += base
        if len(ans) == i:
            ans += '_'
            # if the letter is not in the answer, it shows '_'
    return ans