Meaning: 'Left' means that something remains or is still present after a certain event or time.

Wrong options:

• played: 'Played' is the past tense of 'play,' which does not relate to the context of heat remaining from Earth's formation.
• transformed: 'Transformed' is a past participle indicating a change, which does not fit the context of heat remaining.
• introduced: 'Introduced' suggests bringing something into existence, which does not apply to the concept of heat that has remained.
• backed: 'Backed' implies support or reinforcement, which is irrelevant to the context of heat from Earth's formation.
• clumped: 'Clumped' refers to gathering or clustering, which does not relate to the persistence of heat.

Correct answer: clumped

Explanation: The term 'clumped' is the past participle of 'clump,' indicating that smaller bodies came together during the formation of Earth. This fits grammatically as it follows the conjunction 'and' and aligns contextually with the process of planetary formation.

Meaning: 'Clumped' means to gather or cluster together, particularly in reference to the smaller bodies that formed Earth.

Wrong options:

• played: 'Played' does not fit as it refers to engaging in an activity, which is not relevant to the physical process of formation.
• left: 'Left' is already used in the previous blank and does not fit the context of gathering bodies together.
• transformed: 'Transformed' indicates a change, which does not apply to the act of bodies coming together.
• introduced: 'Introduced' suggests bringing something into existence, which does not accurately describe the process of clumping together.
• backed: 'Backed' implies support, which is not relevant to the context of physical formation.

Correct answer: transformed

Explanation: The word 'transformed' is the past participle of 'transform,' indicating that the energy from collisions changed into heat energy. This fits grammatically as it follows the auxiliary verb 'has' and aligns contextually with the process of energy conversion during collisions.

Meaning: 'Transformed' means to change in form, appearance, or structure, particularly in reference to energy changing into heat.

Wrong options:

• played: 'Played' does not relate to the conversion of energy and is irrelevant in this context.
• left: 'Left' is already used in a previous blank and does not fit the context of energy transformation.
• clumped: 'Clumped' refers to gathering together, which does not apply to the concept of energy changing form.
• introduced: 'Introduced' suggests bringing something into existence, which does not accurately describe the process of energy conversion.
• backed: 'Backed' implies support, which is not relevant to the context of energy transformation.