what the difference between a long position, a long call option, and a future contract

long position means you already get the outright of underlying asset. The company will benefit if value of underlying asset increase. Maxmium loss would be spot price at time 0.

a long call means that you have right to exercise the option at expiration date, or you can just let the option expire. compare with future contract, which you have to pay the forward price at expiration date, the total loss of long call would be premium times corresponding interest.

example, you have two strategy to get the underlying asset in time 1. risk-free interest i.
A: you are into a forward contract with forward price $100 at time 1
B: you buy a europen-style long call with strike price $100 at time 1 for $10.
if the spot price at time 1 is $50,
under forward contract, you still have to pay $100.
under call option, you can just let the option expire, and buy the underlying asset with $50. total loss for this option would be $10(1+i).

In general, a long call can lower the loss, which can be also viewed as insurance against price increases in the underlying asset.

什么优缺点？