将抛物线y=3x²向左平移2个单位，再向下平移1个单位，所得抛物线为(　　)

A：$y=3{\left(x-2\right)}^2-1$

B：$y=3{\left(x-2\right)}^2+1$

C：$y=3{\left(x+2\right)}^2-1$

D：$y=3{\left(x+2\right)}^2+1$