To answer this question, it's important to understand what an isotone is. Isotones are nuclides (a specific type of atom) that have the same number of neutrons but different numbers of protons. The term isotone comes from the root "iso-" meaning same and "-tone" referring to neutrons, similar to how isotope refers to atoms with the same number of protons but different numbers of neutrons.

First, let's figure out the number of neutrons in the given isotope of Germanium $_{32}^{76}Ge$. You can calculate the number of neutrons by subtracting the atomic number (the number of protons, denoted as Z) from the mass number (the sum of protons and neutrons, denoted as A). This gives us:

$$\text{Number of Neutrons} = A - Z$$

For $_{32}^{76}Ge$, this calculation would be:

$$76 - 32 = 44$$

So, $_{32}^{76}Ge$ has 44 neutrons. An isotone of $_{32}^{76}Ge$ would therefore also need to have 44 neutrons. Now, we will calculate the number of neutrons in each option to see which ones match this criteria.

Option A: $_{32}^{77}Ge$

$$\text{Neutrons} = 77 - 32 = 45 \text{ (not an isotone)}$$

Option B: $_{33}^{77}As$ (since the atomic number 33 corresponds to Arsenic, not Germanium)

$$\text{Neutrons} = 77 - 33 = 44 \text{ (is an isotone)}$$

Option C: $_{34}^{77}Se$ (since the atomic number 34 corresponds to Selenium, not Germanium)

$$\text{Neutrons} = 77 - 34 = 43 \text{ (not an isotone)}$$

Option D: $_{34}^{78}Se$ (once again, atomic number 34 is for Selenium)

$$\text{Neutrons} = 78 - 34 = 44 \text{ (is an isotone)}$$