Which of the following improve weld ability of steel?

Correct option is A

​$$\begin{aligned}&\textbf{1. Low Carbon Content (< 0.3\%):} \\&\quad \bullet\ \textbf{Reduces hardness and cracking risk:} \text{ High carbon steels (> 0.3\%) form brittle martensite} \\&\quad\quad \text{during rapid cooling (e.g., welding), leading to cracks.} \\&\quad \bullet\ \textbf{Improves ductility:} \text{ Low-carbon steels (e.g., mild steel) are softer and easier to weld} \\&\quad\quad \text{without pre-/post-heating.} \\[1em]&\textbf{2. Good Affinity to Oxygen:} \\&\quad \bullet\ \textbf{Forms stable oxides:} \text{ Elements like silicon (Si) and manganese (Mn) react with oxygen} \\&\quad\quad \text{to create protective slag (e.g., SiO}_2\text{, MnO), preventing porosity.} \\&\quad \bullet\ \textbf{Prevents porosity:} \text{ Oxygen affinity helps deoxidize the weld pool, reducing defects.}\end{aligned}$$​​