T = int(input())

for _ in range(T):

    # 读取四个选项

    options = [input().strip() for _ in range(4)]

    # 计算每个选项的长度

    lengths = [len(option) for option in options]

    # 选项对应的字母

    letters = ['A', 'B', 'C', 'D']

   

    # 检查是否是三长一短

    min_len = min(lengths)

    min_count = lengths.count(min_len)

    max_len = max(lengths)

    max_count = lengths.count(max_len)

   

    is_three_long_one_short = (min_count == 1 and max_count != 1 )

    is_three_short_one_long = (max_count == 1 and min_count != 1)

   

    if is_three_long_one_short:

        # 找到最短选项的索引

        idx = lengths.index(min_len)

        print(letters[idx])

    elif is_three_short_one_long:

        # 找到最长选项的索引

        idx = lengths.index(max_len)

        print(letters[idx])

    else:

        # 参差不齐，选C

        print('C')