He looks younger ______ his friend; in fact, he is three years senior _______ his friend.
A．to; to B．than; by C．than; than D．than; to
They had just finished the work _______ there was another one waiting for them.
A．while B．when C．as D．since
So far all cloned animals have suffered from some different serious disorders, ______ dying soon after birth.
A．many of which B．many of whom C．many of them D．many of that
We have to give the users something new ________ what we’ve already offered, which is the only way to broaden the appeal of the website.
A．regardless of B．in addition to
C．in exchange for D．according to
Only lately about the dark secrets behind the seemingly-happy marriage of the golf star Tiger Woods.
A．the public have known B．were the public known
C．have the public known D．the public knew
Chemical pollution will bring about a threat to agriculture and food chain, and ________ to human health.
A．frequently B．significantly C．steadily D．consequently
