def extract_arguments(fh):
    datasets = []
    while True:
        line = fh.readline().strip()
        if line == "-1 -1 -1 -1":
            break
        a, b, c, d = map(float, line.split())
        datasets.append((a, b, c, d))
    return datasets

### Explanation

#1. **`extract_arguments(fh)`**:
#    - Reads the input line by line.
#    - Stops reading when it encounters the line `"-1 -1 -1 -1"`.
#    - Converts each line into a tuple of four floating-point numbers representing the latitude and longitude of two cities.
#    - Appends each tuple to the `datasets` list.
#    - Returns `datasets`.
