Which of the following is a pair of coprime numbers?

Coprime numbers are pairs of numbers that have a Highest Common Factor ($\text{HCF}$) of $1$.Let's evaluate each option:Option A: $115$ and $120$ both end in $5$ and $0$, so they are divisible by $5$. $\text{HCF}\ne 1$.Option B: $131$ is a prime number. Let's check if $143$ is divisible by $131$ (it isn't, $143=11\times 13$). The factors of $131$ are $1$ and $131$. The common factor between $131$ and $143$ is only $1$. Thus, $\text{HCF}(131,143)=1$.Option C: $55=5\times 11$ and $121=11\times 11$. Both are divisible by $11$. $\text{HCF}=11\ne 1$.Option D: For $99$ and $141$, the sum of digits of $99$ ($9+9=18$) and $141$ ($1+4+1=6$) are both divisible by $3$, meaning both numbers are divisible by $3$. $\text{HCF}\ge 3\ne 1$.Therefore, $(131,143)$ is the pair of coprime numbers.