Ecology Questions, please help?

1. A frost on the top of mountain has destroyed nearly all vegetations there. The frost would be best described as:
A. the niche of plants
B. the cause of succession
C. the trigger of unfavorable mirco-climate
D. the limiting factor of the ecosystem
E. the cause of inter-specific competition

2. Which one of the following is not a trend in ecological succession?
A. an increase in the number of trophic levels
B. an increase in productivity
C. an increase in community stability
D. a decrease in non-living organic materials
E. an increase in species diversity

3. The pollutants that contribute most to acid rain is:
A. carbon dioxide
B. ammonium
C. ozone
D. sulfur dioxide
E. nitrate and mitrite ions

4. Which of the following is less likely t be an example of secondary succession?
A. Succession occuring in an abandoned rice paddy in Chek Keng
B. Succession after deforestation in Amazon Rainforest
C. Succession after a volcanic eruption in Japan
D. Succession after a flood in the Philippines
E. Succession occuring in a farmland of the Pearl River Delta

5. The organisms which cause red tides in Tolo Harbour belong to:
A.Platyhelminthes
B. Protista
C. Sporozoa
D. Basidiomycota
E. Merostomata

6. Which of the major world biomes(megaecosystems) would have a net primary production(in g/m2 per year) of~2000?
A. Algae beds and reefs
B. Deciduous forest
C. Tropical grassland
D. Estuaries
E. Tropical rain forest

Please help, thx