What is the syntax error in the following simple Puppet configuration file?

class test_class {
file { "/tmp/test.txt":
mode => 600,
owner => root,
group => root
}
}
# Define the node
node testclient {
isa test_class
}

class test_class {
file { "/tmp/test.txt":
mode => 600,
owner => root,
group => root
}
}
# Define the node
node testclient {
isa test_class
}

A.
Comments begin with // character and not a #

B.
The colon (:) after /tmp/test.txt should be a semicolon(;)

C.
Class, node and file section require a semicolon (;) at the end of their definitions

D.
isa should be include