this; these; (commonly pronounced zhei4 before a classifier, esp. in Beijing)[cedict]
套
tàoㄊㄠˋ
cover; sheath; to encase; a case; to overlap; to interleave; bend (of a river or mountain range, in place names); harness; classifier for sets, collections; tau (Greek letter Ττ)[cedict]
追踪
zhuī zōngㄓㄨㄟ ㄗㄨㄥ
to follow a trail; to trace; to pursue[cedict]
系统
xì tǒngㄒㄧˋ ㄊㄨㄥˇ
system[cedict]
不必
bù bìㄅㄨˋ ㄅㄧˋ
need not; does not have to[cedict]
依靠
yī kàoㄧ ㄎㄠˋ
to rely on sth (for support etc); to depend on[cedict]