Which of these was a result of the columbian change

The primary positive effect of the Columbian exchange was the introduction of New World crops, such as potatoes and corn, to the Old World. The most significant negative effects were the transmission of African populations into slavery and the exchange of diseases between the Old and New World.

New lives were possible in America for the poor Europeans

angle a = 40.6°

step-by-step explanation:

for any right angle triangle we know the pythagoras theorem reveals

hypotenuse² = height²+base²

by this formula we will calculate the length of hypotenuse

h² = 6²+7²

⇒ h =√36+49 = √85 = 9.22

now from the given triangle sin a = height/ hypotenuse

                                                sin a = 6/9.22 = 0.651

therefore

so angle a = 40.6°

d. japan's attack on pearl harbor