```tex \documentclass[a4paper,UTF8,twoside]{article} \usepackage{upgreek} \usepackage{tikz-cd} \usepackage{amsmath} \usepackage{amssymb} \usepackage{mathrsfs} \usepackage[margin=20mm]{geometry} \usepackage[colorlinks=true]{hyperref} \def\ds{\displaystyle} \def\ve{\varepsilon} \newcommand{\mcF}{\mathcal{F}} \newcommand{\mcS}{\mathcal{S}} \newcommand{\mrdy}{\,\mathrm{d}y} \newcommand{\mre}{\mathrm{e}} \newcommand{\mri}{\mathrm{i}} \newcommand{\mrpv}{\mathrm{p.v.}} \newcommand{\mrsgn}{\mathrm{sgn}} \newcommand{\swhat}{\ \widehat{}} \begin{document} \begin{tikzcd} \underbrace{Q_t*f}_{{\color{red}A}}\arrow[r]\arrow[d, "\mcF"'] &\underbrace{\overset{{\color{red}\begin{smallmatrix} Mf\\ \|{\triangle}\\ \end{smallmatrix}}}{\dfrac{1}{\uppi}\mrpv\left(\dfrac{1}{x}*f\right)}}_{{\color{red}B}}\arrow[d, "\mcF"'] \arrow[r, equal] &\dfrac{1}{\uppi}\lim\limits_{s\to 0}{\ds\int_{|y|>\ve}}\dfrac{1}{y}f(x-y)\mrdy\\ -\mri\mrsgn(\xi)\mre^{-2\uppi\mri|\xi|}\arrow[r, "\mcS'"] &\underbrace{\left(\dfrac{1}{\uppi}\mrpv\dfrac{1}{x}\right)\swhat}_{{\color{red}C}}\arrow[r, equal, red] &{\color{red}\mri\mrsgn(\xi)} \end{tikzcd} \begin{tikzcd}[column sep=tiny] \underbrace{Q_t*f}_{{\color{red}A}}\arrow[r]\arrow[d, "\mcF"'] &\underbrace{\overset{{\color{red}\begin{smallmatrix} Mf\\ \|{\triangle}\\ \end{smallmatrix}}}{\dfrac{1}{\uppi}\mrpv\left(\dfrac{1}{x}*f\right)}}_{{\color{red}B}}\arrow[d, "\mcF"'] \arrow[r, equal] &\dfrac{1}{\uppi}\lim\limits_{s\to 0}{\ds\int_{|y|>\ve}}\dfrac{1}{y}f(x-y)\mrdy\\ -\mri\mrsgn(\xi)\mre^{-2\uppi\mri|\xi|}\arrow[r, "\mcS'"] &\underbrace{\left(\dfrac{1}{\uppi}\mrpv\dfrac{1}{x}\right)\swhat}_{{\color{red}C}}\arrow[r, equal, red] &{\color{red}\mri\mrsgn(\xi)} \end{tikzcd} \end{document} ``` 第二行的等号过长，请问如何使得第三列左对齐？