So, I'm just wondering which technology my computer booting with whether it's BIOS or UEFI. Here is the tool that I found useful to help me achieve that goal: efibootmgr.
1. Install efibootmgr:
$ sudo apt-get install efibootmgr
2. Check if my computer's using UEFI to boot:
$ sudo efibootmgr
if the result is as following:
EFI variables are not supported on this system.
the answer is NO.
For more information about UEFI, please read this article: https://www.happyassassin.net/2014/01/25/uefi-boot-how-does-that-actually-work-then/