In the early days of germ theory, contagious diseases were thought to be caused by fungi or bacteria. in the 1890s, dmitri ivanovski filtered extracts from diseased tobacco plants and discovered that the disease could be transmitted to new plants through the filtrate. he concluded that the disease was caused by particles smaller than bacteria: the tobacco mosaic virus.

B

Explanation:

He used a new experimental method to test his hypothesis.

the two answers are a, the population of birds with large beaks will increase on the island, and c, the trait for large beaks will be passed on to future generations through natural selection. the reason for that is because if the birds that have beaks developed for eating small seeds lose all of their food, they will go hungry and eventually starve because they physically cannot eat the large seeds, therefore making the population of large beaked birds higher. also, if the trait of large beaks are dominant on the island over small beaks, then over time the large beaked birds will reproduce more and more, while the smaller beaked birds will reproduce less and less because they can't survive with the food provided. that leads to the trait of small beaks disappearing and the trait of large beaks taking over the island.