The original sentence uses the incorrect quantity expression “the amount” rather than the appropriate “the number” to describe the countable noun “systems.” The construction “the amount” can be used to describe only non-countable nouns, such as “water,” “ice,” and “information,” while "the number" can be used to describe countable nouns. Furthermore, the original sentence uses the incorrect expression “more expensive” to describe “prices.” While goods or services can be more or less expensive, their prices can be only higher or lower.

For example, you wouldn't say "This price is more expensive than that one"; instead, you would say "This price is higher than that one."

• (A) This choice is incorrect as it repeats the original sentence.

• (B) CORRECT. This answer choice supplies the proper quantitative expression “the number” to refer to the countable noun “systems” and replaces the incorrect phrase “more expensive” with the proper adjective “higher” that should be used to describe “prices.”

• (C) This answer choice uses the incorrect phrase "the numbers of." Correct phrases can include the plural "a number of" or the singular "the number of" (which is the correct usage in this sentence) but will never include "the numbers of."

• (D) This answer choice uses the incorrect expression “more expensive” to describe “prices.” While goods or services can be more or less expensive, their prices can be only higher or lower.

• (E) This answer choice uses the incorrect quantity expression “the amount” rather than the appropriate “the number” to describe the countable noun “systems.” The construction “the amount” can be used to describe only non-countable nouns, such as “water,” “ice,” and “information.”