گزینه (۱) درست است.

$\overline{a_ra_{r-1}...a_28}\times4=\overline{8a_ra_{r-1}...a_2} \Rightarrow a_2=2 \\ \Rightarrow \overline{a_2a_{r-1}...a_328}\times4=\overline{8a_r...a_32} \Rightarrow a_3=1 \\ \Rightarrow \overline{a_r...a_4128}\times4=\overline{8a_r...a_412} \Rightarrow a_4=5 \\ \overline{a_r...a_55128}\times4=\overline{8a_r...a_5512} \Rightarrow a_5=0 \\ \Rightarrow \overline{a_r...a_605128}\times4=\overline{8a_r...a_60512} \Rightarrow a_6=2 \\ \Rightarrow \overline{a_r...a_7205128}\times4=\overline{8a_r...a_720512} \Rightarrow a_7,a_8,...= there is not \\ \Rightarrow number=205128 \Rightarrow a_{r-1}=a_5=0$