Dr. Smith will never leave his parents ________ he is sure both of them are taken good care of.
A.since B.though C.if D.unless
China has successfully prevented the Covid-19 from _______ through the country.
A.spread B.to spread C.spreading D.spreads
—Why are you so sleepy?
—Because I ______to prepare for the English test last night.
A.put up B.went up C.set up D.stayed up
It is 4:30p. m. Ben and Leon _______their work, so they are playing chess now.
A.finish B.were finishing C.have finished D.will finish
As middle school students, we follow the public rules wherever we go.
A.would B.should C.might D.could
Life on Mars would be interesting ________ challenging.
A.as well as B.as long as C.as good as D.as soon as
