The pick pocket was brandishing a knife.

using
pointing
showing
waving

The correct answer is A. using.

To brandish something means to wave it about in a threatening or aggressive way. In this case, the pickpocket was using a knife to threaten someone.

The other options are not as accurate. To point something means to direct it towards someone or something. To show something means to present it to someone so that they can see it. To wave something means to move it back and forth in the air, often as a greeting or to attract attention.

In this case, the pickpocket was not pointing, showing, or waving the knife. He was using it to threaten someone.