**Answer:**

**Explanation:**

First, you need to find the **empirical formula** of the compound (histamine).

To find the empirical formula convert all the data given in mass units (miligrams) into mole numbers.

You do that by using the formula: number of moles = mass in grams / atomic mass.

To find the mass in grams divide the mass in miligrams by 1,000.

Build a **table**:

Element mass (g) atomic mass (g/mol) number of moles (mol)

C 0.208 12.011 0.0173

H 0.031 1.008 0.0307

N 0.146 14.007 0.0104

Now, find the **ratio C:H:N**, for which you divide every number of moles by the smallest number of moles: 0.0104:

- C: 0.0173 / 0.0104 = 1.665

- H: 0.0307 / 0.0104 = 2.957

- N: 0.0104 / 0.104 = 1.002

You must find a multiple that yields 1.665 to a reasonably close integer.

Muliply every amount by 3:

Hence, the **empirical formula** is C₅H₉N₃.

Now, find the **mass of the empirical formula**:

- 5(12.011 g/mol) + 9(1.008 g/mol) + 3(14.007 g/mol) = 111.148 g/mol ≈ 111 g/mol.

Since the mass of the empirical formula is the same of the molecular formula, both formulae are the same.

Therefore, the answer is: C₅H₉N₃ **← molecular formula**