Which cards are equivalent to 1/2+6/9? Choose ALL the correct answers.

What is the result of the greenhouse effect? a. heat is deflected from the atmosphere. b. heat is released from the atmosphere. c. heat is kept in the atmosphere. d. plants are able to grow in the tropics where the air is the heaviest.

How many countries have portuguese as a national language?

Given: circle a externally tangent to circle b. how many possible common tangents to circles a and b can exist? 2 3 4