the answer is B 4-6 months thats when they can pick up large objects.
<em>im confused hold on imma send you a link to the answer</em>Explanation:
Answer:Three elements make up over 99.9 percent of the composition of dry air: these are nitrogen, oxygen, and argon.
Explanation:
Answer:


Explanation:
Wave 1, 
Wave 2, 
Wave 3, 
Wave 4, 
The general equation of travelling wave is given by :

The value of
will remain the same if we take phase difference into account.
For first wave,



For second wave,



For the third wave,



For the fourth wave,



It is clear from above calculations that waves 1 and 3 have same time period. Also, wave 2 and 4 have same time period. Hence, this is the required solution.