Vulcanised rubber, celluloid and plastic - these materials were, _____ a certain degree/extent, invented by accident.

Many birds have special SIGNIFY for humans but none is perhaps more respected than the owl.

For centuries, people existed in isolated COMMUNE far from one another.

Tom and Alexis said "We're getting married in May." //ANNOUNCED// Tom and Alexis . . . in May.

Some countries are in favor of abolishing leap seconds while others ARGUE/DISAGREE/DISPUTE/QUESTION that the technical challenges are manageable.

As all school children know, there are 60 seconds in a minute. But every so often, our planet EARNS/GAINS/WINS/OBTAINS a second.

HISTORY, there have been long periods when one might barely detect a single change in pronunciation.

As it's also a good guide to people's innermost THINK, learning how to "read" these would be a valuable life skill.

Being completely honest about your opinions isn't always advisable./IDEA// It isn't . . . completely honest about your opinions.

He described this time as like a prison sentence with harsh, TOLERATE conditions.

It's 7pm and I'm sitting in a café I've never been in before. It's CRAMMED/CRUSHED/MASSED/PILED with people, but nobody's talking.

But this chance discovery of useful materials _____ undergoing a change.

Last night, I foolishly left my apartment without a key and couldn't get back in. //LOCK// Last night, I was foolish enough . . . my apartment.