A few electric field lines for a system of two charges Q_1 and Q_2...

From the behaviour of electric lines, we can say that $Q_1$ is positive and $Q_2$ is negative. Further, \left|Q_1\right|>\left|Q_2\right| At some finite distance$to the right ofQ_2$, electric field will be zero. Because electric field due to $Q_1$ is towards right (away from $Q_1$ ) and due to $Q_2$ is towards \left(towards $Q_2$ ). But since magnitude of $Q_1$ is more, the two fields may cancel each other because distance of that point from $Q_1$ will also be more. $\therefore$ The correct options are (a) and (d).