Use the correct tense or form ef the verb given in each

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VE. Use the correct tense or form ef the verb given in each sEKtence. (i pt)
29. The Earth
for billions of years. (exist)
io save electricity. (usc)
30. They suggested energy-saving bulbs
31. Mary
her homework with great care all the time. (du)
since last week. (not rain)
32. 1t