In the following passage some words have been deleted. Fill in the blanks with the help of the alternatives given. Select the most appropriate option for each number.
Human activities are changing Earth's natural greenhouse1. ______. Burning fossil fuels like coal and oil puts 2. ______ carbon dioxide into our atmosphere. NASA has 3. ______ increase in the amount of carbon dioxide and some other greenhouse gases in 4. ______ atmosphere. Too much of these greenhouse gases can 5. ______ Earth's atmosphere to trap more and more heat. This causes Earth to warm up.
Select the most appropriate option to fill in the blank No. 3.
In the following passage some words have been deleted. Fill in the blanks with the help of the alternatives given. Select the most appropriate option for each number.
Human activities are changing Earth's natural greenhouse1. ______. Burning fossil fuels like coal and oil puts 2. ______ carbon dioxide into our atmosphere. NASA has 3. ______ increase in the amount of carbon dioxide and some other greenhouse gases in 4. ______ atmosphere. Too much of these greenhouse gases can 5. ______ Earth's atmosphere to trap more and more heat. This causes Earth to warm up.
Select the most appropriate option to fill in the blank No. 3.
Observing
Observing
to observe
to observe
Observe
Observe
Observed
Observed
Correct Answer:
Observed
Observed
option D is the right answer here,
In order to form the present perfect tense, we use the word have or has followed by the past participle of the verb
so the word has/have are always followed by the third form of the verb.
so option D observed is correct here