Which of the following has a charge of +1 and a mass of 1 amu ?

The particle that has a charge of +1 and a mass of 1 atomic mass unit (amu) is a proton.

Here are the steps to answer this question:

1. Understand the question: The question is asking for a particle that has a specific charge and mass.

2. Recall the properties of subatomic particles: There are three main subatomic particles - protons, neutrons, and electrons. Protons have a positive charge, neutrons have no charge, and electrons have a negative charge. The mass of a proton and a neutron is approximately 1 amu, while the mass of an electron is much smaller.

3. Match the properties: The particle that matches the properties given in the question (charge of +1 and mass of 1 amu) is a proton.

So, the answer is a proton.