Direction: In the following passage, some of the words have been left out. First read the passage over and try to understand what it is about. Then fill in the blanks with the help of the alternatives given.

Just sixty-five million years ago our ancestors were the most unprepossessing of mammals-creatures with the size and intelligence of moles or tree shrews. The earth then (461) full of awesome, nightmarish lizards which (462) virtually every ecological niche. Some of (463) had very large brains, an upright (464) and two little front legs very much (465) hands, which they used dexterously to (466) small animals for dinner. But then (467) did not survive. Sadly, in one (468) event every one of them was (469) . And no one knows what wiped (470) the dinosaurs.