0 Hi elviajero 02br 02br 00when using a verb form with 'ing'(as in the first sentence above) you can omit 'who+be' and 'that+be' after scientists 02br 00Consequently, #3 and 4 are correct and completely acceptable: 'who' refer to persons, such as scientists, and 'that' can also refer to persons though it is more acceptable to use 'who' in this case. 02br 00about the double and single quotes, I don't know the differences... 0-
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