How to bold font in Latex & how to make circle serial number

1.latex How to bold fonts in ？

\textbf{
     Text }

Let's give you an example :

\textbf{
     Say formally ,PCA What we do is to find a low dimensional plane , Then project the data onto it .}

2. How to make a circle number
If the serial number is not large, you can use \ding{172}---\ding{180} To express ：
example ：

\ding{
    172}

\ding{
    173}

\ding{
    174}