Let's go through the questions one by one.

Question 17:

For the children's holiday activity, the group must meet two conditions:

1. The minimum ratio of adults to children is 1:4.
2. The ratio of boys to girls must be either 1:2 or 2:1.

Now, let's check each group.

Group A:

• Number of adults = 3
• Number of boys = 6
• Number of girls = 4
• Total children = 6 boys + 4 girls = 10
• Ratio of adults to children: $\frac{3}{10}$. This is less than $1:4$ (or $\frac{1}{4}$), which means Group A does not meet the adult-to-child ratio.

Group B:

• Number of adults = 4
• Number of boys = 8
• Number of girls = 8
• Total children = 8 boys + 8 girls = 16
• Ratio of adults to children: $\frac{4}{16} = \frac{1}{4}$. This meets the adult-to-child ratio.
• Ratio of boys to girls: $\frac{8}{8} = 1:1$, which does not meet the required ratio of either $1:2$ or $2:1$.

Group C:

• Number of adults = 5
• Number of boys = 15
• Number of girls = 5
• Total children = 15 boys + 5 girls = 20
• Ratio of adults to children: $\frac{5}{20} = \frac{1}{4}$, which meets the adult-to-child ratio.
• Ratio of boys to girls: $\frac{15}{5} = 3:1$, which does not meet the required ratio.

Group D:

• Number of adults = 6
• Number of boys = 16
• Number of girls = 8
• Total children = 16 boys + 8 girls = 24
• Ratio of adults to children: $\frac{6}{24} = \frac{1}{4}$, which meets the adult-to-child ratio.
• Ratio of boys to girls: $\frac{16}{8} = 2:1$, which meets the required ratio.

Thus, Group D meets both the adult-to-child and the boys-to-girls ratio.

Question 18:

Lydia's argument is that social media and phone use are contributing to a mental health crisis, particularly due to its interference with sleep and emotional issues.

To strengthen her argument, we are looking for a statement that links social media use or phones with a negative impact on health or emotional well-being. Let's review each option:

• A: "Social media has allowed teens to make more friends." This would weaken Lydia's argument as it shows a positive effect.
• B: "Using phones allows people to become more organised." This also weakens her argument, as it highlights a benefit of phone use.
• C: "Social interactions can improve mental health." While social interaction is important, it does not directly support Lydia's point about the negative effects of phone or social media use.
• D: "Not all teens have access to phones." This strengthens Lydia's argument, because it suggests that the mental health issues she describes could be linked to those teens who do use phones or social media excessively, while those without access might not face the same problems.

Thus, the correct answer is D, as it strengthens Lydia's argument.

Do you need more details or have any questions?

Here are 5 questions that can help expand your understanding:

1. How does the ratio of adults to children in a group impact safety or supervision in activities?
2. Why is it important to maintain a specific ratio of boys to girls in a group setting?
3. How does the use of social media affect teens' mental health in modern studies?
4. What are some common arguments for and against social media's impact on teen well-being?
5. Could limiting phone usage in teens improve their sleep patterns and emotional health?

Tip: Always double-check ratios by simplifying them to their lowest form to ensure clarity in comparison.