## Core Concept
The question pertains to the concentration of fluoride in toothpaste, specifically when it is stated as 700 ppm (parts per million). This measurement is crucial in dentistry for the prevention of tooth decay and understanding the potential risks of excessive fluoride intake.

## Why the Correct Answer is Right
To determine the amount of fluoride in a toothpaste with 700 ppm fluoride, we need to understand what ppm signifies. Parts per million (ppm) is a measure of concentration, equivalent to milligrams per liter (mg/L) or milligrams per kilogram (mg/kg). Therefore, a toothpaste with 700 ppm fluoride contains 700 milligrams of fluoride per kilogram of toothpaste. When considering a standard 100g (or 0.1 kg) tube of toothpaste, the calculation would be: 700 mg/kg * 0.1 kg = 70 mg of fluoride.

## Why Each Wrong Option is Incorrect
- **Option A:** Without a specific value, it's not possible to directly refute this option, but we can assess its validity based on calculations.
- **Option B:** Similarly, lacks a specific value for direct comparison.
- **Option C:** This option suggests 0.07 mg, which seems too low given the 700 ppm concentration and a reasonable quantity of toothpaste.
- **Option D:** This option indicates 70 mg, aligning with our calculation for a 100g tube of toothpaste with 700 ppm fluoride.

## Clinical Pearl / High-Yield Fact
A crucial point to remember is that the recommended fluoride concentration in toothpaste for children and adults varies, but generally, a concentration of around 1000 ppm is often recommended for adults and children over 6 years. However, for children under 6, a lower concentration (around 500 ppm) is often advised to minimize the risk of dental fluorosis. Understanding ppm and its implications for fluoride intake is vital for both dental health professionals and patients.

**Correct Answer:** D. 70 mg.