Better method for preparation of BeF2, among the following is:
(1) $\left(\mathrm{NH}_4\right)_2 \mathrm{BeF}_4 \xrightarrow{\Delta} \mathrm{BeF}_2$
(2) $\mathrm{BeH}_2+\mathrm{F}_2 \xrightarrow{\Delta} \mathrm{BeF}_2$
(3) $\mathrm{Be}+\mathrm{F}_2 \xrightarrow{\Delta} \mathrm{BeF}_2$
(4) $\mathrm{BeO}+\mathrm{C}+\mathrm{F}_2 \xrightarrow{\Delta} \mathrm{BeF}_2$