Give the correct form of the bracket words

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VII. Give the correct form of the bracketed words
When it rains, it does not always pour. During a typical storm, a (1. compare) small amount of the lock-up moisture in each
cloud reaches the ground as rain. So the idea that human intervention - a rain dance, perhaps - might encourage the sky to
give up a little (2. add) water has been around since prehistoric times. More recently, would-be rain makers have used a
more direct procedure - that of throwing (3. vary) chemicals out of aero-planes in an effort to wring more rain from the clouds,
a practice known as "cloud seeding". Yet such techniques, which were first developed in the 1940s, are (4. notoriety) difficult
to evaluate. It is hard to (5. certain), for example, how much rain would have fallen anyway. So, despite much anecdotal
evidence of the advantages of cloud seeding, which has led to its adoption in more than 40 countries around the world, as
far as scientists are concerned, results are still (6. conclusive). That could be about to change. For the past three years
researchers have been carrying out the most extensive and (7. rigor) evaluation to date of a revolutionary new technique
that will substantially boost the volume of (8. rain). The preliminary (9. find) of their experiments indicate that (10. solidify)
evidence of the technique's effectiveness is now within the scientists' grasp.