Self-fertilization is avoided in sponges because
a. there is no way for sperm to enter the sponge.
b. the sperm do not possess the enzyme needed to penetrate the egg.
c. sperm and eggs are not produced at the same time.
d. none of the above is true; self-fertilization is common in sponges.

In 2015, about ten percent of total u.s. energy consumption was from renewable energy sources. renewable energy plays an important role in reducing greenhouse gas emissions. when renewable energy sources are used, the demand for fossil fuels is reduced. sanjay and his family want to cut back on their use of non-renewable resources at home. they are thinking of an alternate way to heat their home without adding more greenhouse gases or pollutants to the environment. which renewable resource would not fit into their plan? a) solar power b) burning wood c) constructing a wind turbine eliminate d) generating hydroelectric power