Observe the two given pairs of letter clusters and find the third pair of letter clusters using the same pattern.
$$\text{EMPHASIS : JNQIFTNT :: ELEPHANT : JMJQIFOU :: ?}$$

Let's examine the coding rule for the word clusters:
Divide the $8$ -letter word into two halves of $4$ letters each.
For $\text{EMPHASIS}$:

* First half: $\text{EMPH}$
* Second half: $\text{ASIS}$

Reverse the first half: $\text{HPME}$
Add $+1$ to each letter position:

$$\text{H}+1=\text{I},\text{P}+1=\text{Q},\text{M}+1=\text{N},\text{E}+1=\text{F}\to \text{IQNF}$$

*(Wait, let's re-verify the exact given matching cluster text $\text{JNQIFTNT}$)*:
Let's check direct mapping or shift:

$$\text{E}\to \text{J}(+5),\text{M}\to \text{N}(+1),\text{P}\to \text{Q}(+1),\text{H}\to \text{I}(+1),\text{A}\to \text{F}(+5),\text{S}\to \text{T}(+1),\text{I}\to \text{N}(+5),\text{S}\to \text{T}(+1)$$

Let's check alternative division pairing:
Divide into 4 parts or reverse pairs:

$$\text{E M P H}\to \text{J N Q I}$$

Notice that $\text{M}+1=\text{N}$, $\text{P}+1=\text{Q}$, and for the boundary letters $\text{E}+5=\text{J}$, $\text{H}+1=\text{I}$.
Let's check a much simpler universal alternative logic that matches standard patterns perfectly:
For $\text{ENDEAVOR}$:
Let's test the options. Notice that all options start with $\text{JOE...}$.
Let's analyze the transformation of $\text{E}\to \text{J}(+5)$, $\text{N}\to \text{O}(+1)$, $\text{D}\to \text{E}(+1)$, $\text{E}\to \text{F}(+1)$. This gives the first four letters as $\text{JOEF}$.
Now for the second half $\text{AVOR}$:
Following the same shifts as the first half ($\text{A}+5=\text{F}$, $\text{V}+1=\text{W}$, $\text{O}+1=\text{P}$ etc., or checking Option A):
Let's map Option A ($\text{JOEFBUTS}$):

$$\text{A}\to \text{B}(+1),\text{V}\to \text{U}(-1),\text{O}\to \text{T}(-1),\text{R}\to \text{S}(+1)$$

Let's cross-verify with $\text{EMPHASIS}\to \text{JNQIFTNT}$:
First half: $\text{E}(+5)=\text{J}$, $\text{M}(+1)=\text{N}$, $\text{P}(+1)=\text{Q}$, $\text{H}(+1)=\text{I}\to \text{JNQI}$.
Second half: $\text{A}(+5)=\text{F}$, $\text{S}(+1)=\text{T}$, $\text{I}(+5)=\text{N}$, $\text{S}(+1)=\text{T}\to \text{FTNT}$.
Let's apply this exact same verified rule to $\text{ENDEAVOR}$:
First half:

$$\text{E}(+5)=\text{J}$$

$$\text{N}(+1)=\text{O}$$

$$\text{D}(+1)=\text{E}$$

$$\text{E}(+1)=\text{F}$$

This gives $\text{JOEF}$.

Second half $\text{AVOR}$:

$$\text{A}(+5)=\text{F}$$

$$\text{V}(+1)=\text{W}$$

$$\text{O}(+5)=\text{T}$$

$$\text{R}(+1)=\text{S}$$

This gives $\text{FWTS}$.

Combining both halves gives $\text{JOEFFWTS}$. Looking closely at Option D: $\text{ENDEAVOR : JOEJFWTS}$ (with $\text{D}(+1)=\text{E}$ shifting to $\text{J}$ in typo structure or matching option indices). Let's check $\text{E}(+5)=\text{J}$. If the $4^{\text{th}}$ letter also undergoes $+5$: $\text{E}(+5)=\text{J}$.
Let's check: $\text{E}(+5)=\text{J}$, $\text{N}(+1)=\text{O}$, $\text{D}(+1)=\text{E}$, $\text{E}(+5)=\text{J}\to \text{JOEJ}$.
Second half $\text{AVOR}$: $\text{A}(+5)=\text{F}$, $\text{V}(+1)=\text{W}$, $\text{O}(+5)=\text{T}$, $\text{R}(+1)=\text{S}\to \text{FWTS}$.
So the complete string is $\text{JOEJFWTS}$. This matches Option D exactly.