Each of the login ways is not perfect, as the system may be fooled in a certain way. The biometric data is an exclusion, but can still be fooled sometimes (especially when the hardware is poor). However, their combination exponentially decreases the chance of malfunctioning or hacking. When you combine a strong password, biometric auth and a control question, it is almost impossible to get in. However, for personal security a long and mixed password together with the confirmation from the other device is enough for the invulnerable protection.