Answer:
A
Step-by-step explanation:
The standard cosine function has the form:

Where |<em>a</em>| is the amplitude, 2π / <em>b</em> is the period, <em>c</em> is the phase shift, and <em>d</em> is the vertical shift.
We have the function:

We can rewrite this as:

Therefore, <em>a</em> = 2, <em>b</em> = 3, <em>c</em> = -2π/3, and <em>d</em> = 1.
Our phase shift is represented by <em>c. </em>Thus, the phase shift is -2π/3.
Our answer is A.