When you have a question about fact or opinion, look carefully at what can be proven and if there are words in the sentence which reflect opinion. For example, the first sentence is fact which can be proven in any pizza place. The third sentence is also fact which you can prove in any flower garden or field. The second sentence, however, contains the words "more interesting" which reflects opinion. Think of whether you find basketball more interesting than golf. Do any of your friends dislike watching any sport? In whose opinion is basketball a more interesting sport to watch? Yours? Your best friends? This is a classic example of opinion. Learn to look for words which signal opinion such as the "more interesting" in this example.
The first two statements are opinions, because they have a certain amount of bias in them. The last statement can be proved therefore it is a fact.
1) Many people order pepperoni on their pizzas...is an opinion as you dont know what people order on their pizza, someone could be vegetarian and refuse to get pepperoni on their pizza
2) Basketball is more interesting to watch than golf...opinio (as stated by mizzwillie)
3) Flowers bloom in the spring and summer months....fact as it is soemthing that can be proven