Chemistry Practical

Which of the following statement(s) is( are) correct?
Which of the following is(are) correct?
$$CaCO_3\xrightarrow{\Delta}A+B(gas)$$

$$A+H_2O\longrightarrow C$$

$$\begin{matrix}C&+&B&\longrightarrow&D&+&H_2O\\&&&&(White\:ppt.) \end{matrix}$$

$$\begin{matrix}D&+&B(gas)&\longrightarrow&E&\xrightarrow[BaCl_2]{Boil}&F\\&&&&(Water\:soluble)&&(White\:ppt.)\end{matrix}$$

Select the correct option(s) for white ppt. shown in the above reactions :
Pick out the correct statement(s) :