$Eg: bbs|r_{0}|3| 2000$
$r_{0}=FCH$
$r_{0}:1111\underline{1}100\ (pos=3)$
$if\ 3^{rd}\ bit: 0\ PC=Sequence\ address$
$if\ 3^{rd}\ bit: 1\ PC=2000$
$temp\leftarrow reg\&mask$
$let's\ Test:$
$1)$
$mask: 00001000$
$r_{0}:\ \ \ \ \ \ \underline{11111100}\ (pos=3)$
$temp:\ 00001000\ (08H)$
$Analysis:$
$In\ pos=3\ we\ got\ 1 // condition\ true$
$In\ temp\ we\ got\ non-zero\ result // condition\ true$
$2)$
$mask: 00001000$
$r_{0}:\ \ \ \ \ \ \underline{11110110}\ (pos=3)$
$temp:\ 00000000\ (00H)$
$Analysis:$
$In\ pos=3\ we\ got\ 0 // condition\ false$
$In\ temp\ we\ got\ zero\ result // condition\ false$
$3)$
$mask: 01101101$
$r_{0}:\ \ \ \ \ \ \underline{11110110}\ (pos=3)$
$temp:\ 01100100\ (64H)$
$Analysis:$
$In\ pos=3\ we\ got\ 0 // condition\ false$
$In\ temp\ we\ got\ non-zero\ result // condition\ true$
Now go through Options
$d)\ mask\leftarrow 0xf: Multiple\ 1's\ in\ mask\ \times$
$c)\ mask\leftarrow pos: Multiple\ 1's\ in\ mask\ \times$
$like\ pos=3(11), pos=5(101)$
$b)\ mask\leftarrow 0xffffffff>>pos: Multiple\ 1's\ in\ mask\ \times$
$a)\ mask\leftarrow 0x1<<pos:\checkmark$
$mask\leftarrow 00000001<<3$
$mask\leftarrow 00001000$
Variable mask must be generated by option $a)$ for correct emulation