There is only one guaranteed way to be sure if you are vitamin B12 deficient and that is to get your doctor to prescribe you high dose vitamin B12 injections and see if your health improves in the long term.

Surrender is no guarantee that an armed police officer will not shoot you.

I can guarantee you that my mistakes far outweigh my achievements because a single achievement is the fruition of many mistakes.

If the government had been set up to guarantee a minimum subsistence allowance to all adults and children, COVID-19 would not have caused so much mayhem.