Why does this file give syntax error in verilog?
You need to read the FAQ.

Specifically, the $ commands need to be in an initial block, to wit:

`include "ask.v"

module t_circuit_320a_delay;
    wire N,F;
    reg A,B,C,D;

  circuit_320a M1 (A,B,C,D,N,F);

  initial begin
     A=1'b0; B=1'b1; C=1'b0; D=1'b1;
  end

  initial #200 $finish;

  initial begin
    $dumpfile("ask.vcd");
    $dumpvars(0, t_circuit_320a_delay);
  end

endmodule


It will also help if you instantiate the correct module. t_circuit_320a_delay should be instatiating circuit_320a, not itself, and the $dumpvar call needs to refer to t_circuit_320a_delay, not the name of the file.