National parks can be a double-edged sword because

The given blank can be filled with that the crowds of people, which are attracted can disrupt the ecosystem.

Explanation:

The national parks can be regarded as a double-edged sword as the individuals, which visits the park can also harm the park's ecosystem. The main motto of the establishment of the national parks is to provide protection to the species and the ecosystem from the destruction done by human beings.  

Therefore, certain measures are needed to be taken in order to minimize the destruction, like limiting the daily limits of the crowd, or by enhancing the price of the tickets. Safety measures like security should be increased in order to keep an eye on the crowds. Ultimately reminding the people about the importance and privilege attained by the national parks.  

it's unlikely a majority of a large population would agree on issues

hope this : )

ans.

gregor john mendel is known for study of inheritance in pea plants. he used garden pea plant for his study, having alternative traits for various characters. he performed cross-breeding in pea plants to check how characters are transmitted between parents to offspring, such as cross between pure tall and pure dwarf plant. mendel studied the inheritance patterns in pea plants for various generations.

thus, the correct answer includes options and f).